It seems that there is this belief, mostly amongst non-Goths, that Goth is seen as an identity people take on in order to be visibly rebellious against a middle-class upbringing, and that for Goths past university age that it is a variation on being a "trustafarian". This, I think, misinterprets the motivations of those who become Goth - it is not done as an active rejection or rebellion of anything, simply as the enjoyment of music, fashion and art outside the mainstream. It has become a subculture, but it is not a counterculture in the way of Punk or Hippie - Goth is more concerned with arts than politics, especially music.
In seeking artistic fulfilment, whether musical, fashion-related, visual, or otherwise, in taboo areas such as lyric content about death, dark romance and the occult or in macabre art or in clothes, accessories and a personal appearance that are easily identifiable as different from the mainstream, the mainstream then perceives Goths engaged in an active rebellion against them, rather than simply preferring something else. As a large proportion of contemporary Goths come from a middle-class background, Goth has become viewed as something done by disaffected middle-class youths trying to assert independence and difference from their middle-class upbringings. Goth, though, is not a middle-class phenomena, it is a cross-class phenomena, and one that grew out of Punk, a subculture once seen as working-class.
I think part of the reason that Goths tend to be seen as middle-class pseudo-rebels is the fact that unlike other subcultures, Goth is not a counterculture, and therefore not incompatible with dominant western culture (not having talked to any goths in the Middle East, Africa or the Far East, or been there myself I cannot comment on their experiences) because while it does tend to be more tolerant towards things such as having a radically different appearance, being interested in non-mainstream and occult spirituality, and not adhering to gender norms, and in looking for beauty in places otherwise considered taboo, it does not have a political or cultural group of accepted beliefs. Whether a person holds beliefs counter to those upheld by the mainstream, or more radical than those of the mainstream or even in accordance is up to the individual, and not related to subcultural affiliation.
One of the ways that Goth is different to the mainstream in terms of values is the importance of self-made cultural signifiers over bought cultural signifiers - Goths tend to value someone sewing their own bustle-skirts and fancy jackets over them being bought, and while judgement may be passed on the quality of the final product by some, the desire to create for oneself will be lauded, not just for the skill required, but because creating emancipates one from having to buy into mass-produced concepts and allows for originality and a heightened level of freedom of expression bound only by courage and skill. Making one's own clothes has often been mocked as either being a forced condition of poverty (strange in a country where it is cheaper to get clothes from a discount retailer such as Primark or from a charity shop than it is to buy materials to make clothes, although this does not necessarily stand for alternative clothes - it is cheaper to buy a t-shirt than to make one, it is cheaper to make a bustle gown than to buy one) or an attempt to be deliberately countercultural - i.e simply doing so because the mainstream isn't - rather than simply as a way to have clothes that fit correctly and look exactly the way the wearer intends, or at least hopefully rather close to that vision.
Goths may also have a tendency to end up socio-economically as middle class, regardless of their backgrounds, because there is tendency for us to be more intellectually or academically inclined. I was certainly a bookish, academic sort at school, the sort that was skipped a year and went to literature and chess clubs as well as pursuing various musical interests, despite having survived childhood abuse and coming from a low-income single-parent household, and many of my Goth friends are either in academia as a career or have gone through higher education in the more intellectually challenging fields, and some of those despite coming from backgrounds that could be considered "challenging" or "disadvantaged" and others from a rather varied selection of backgrounds, but my personal experiences do not speak for all. While the economy is struggling in my country at least, it still stands that having a degree or two in a subject that is applicable to specialist industries is certainly useful in terms of career prospects and thus socio-economic status. Goths also tend to have a certain level of self-determination which gives them the courage to defy convention enough to wear alternative clothes or listen to non-mainstream music, but also gives them a level of ambition and direction.
Also, some of the more visible Goths, and thus the ones that are noticed by non-Goths and the mainstream, are going to be the ones with the more elaborate or polished appearances, and terms of items such as jewellery, boots and unusual clothing, if bought these can be rather expensive, unaffordable to the poor or working class without very careful saving. Also, to the outside, those who have self-made outfits that are highly elaborate and have considerable skill in their creation maybe assumed to have bought them simply because it is perceived that ordinary people simply don't have the skill to make clothes and accessories like that any more, and that these are antiquated crafts lost to history. When non-Goths ask me about items I have made myself, or even modified, there is a continual reaction of shock that I really did make something myself, that it wasn't produced in a factory or produced in a factory the way it now is. Goths tend to place higher value on something being aesthetically pleasing than expensive, and, as mentioned before, on crafting and creating for oneself, so outfits that look expensive may be, but at the same time, they may be made from recycled charity shop clothes on a budget sewing machine (at least mine are).
Some Goths do hold an antagonism towards the mainstream, at least partly because Goths do come on the receiving end of unpleasantness from non-Goths, and this is then perceived as representative of the mainstream attitude towards Goths, although that attitude actually varies widely dependent on location and current trends, and of course, is incredibly diverse on an individual level. There are those amongst the Goth subculture that do hold views not really in accordance with the mainstream (or the local mainstream) and who do have views critical of modern western society (I certainly do) and who use the subculture as a vessel for their countercultural beliefs. There are also those who do see Goth as a vehicle for youthful rebellion, or a way to assert their identity as separate from that of those around them, or simply to antagonise their parents and things they see as "the establishment". None of these facets, though, is representative of the subculture as a whole, and can even be seen as an appropriation of the subculture for a personal agenda (and in the case of those appropriating the subculture for antagonistic shock value, or for garnering attention, doing so in a damaging and negative way).
I think there is also an assumption that in order to have the time to actually ponder concerns like the one I am writing about, or to "indulge" in the arts or music, that one must be at least middle class-because it is assumed that otherwise I would be too busy trying to make a living. At one point I was at college, working in a supermarket, and going to evening classes - I wrote observational poetry in the quiet moments in the supermarket, on the back of discarded receipts. While an active pursuit of the arts, like learning a musical instrument from a teacher, or going to concerts and the sorts of exhibitions where you have to pay, does require financial resources, it is possible to be personally involved and interested in the arts with little in the way of resources. I taught myself to play piano, partly because I could not afford a tutor, and yes, it took a long time, and yes, my technique is highly unorthodox (and probably self-defeating on occasion) but I can now play things with relative competency and musicality, I draw on cheap office paper with the biros that are given away free in banks or with catalogues, I make and modify my fashion out of things I bought in charity shops. A passion for creativity may be bracketed in terms of its final form by resources and circumstance and opportunity, but not in its existence. Goth, as a subculture focused on artistic expression, especially music, is therefore bracketed only in form by resources, not in vision, passion or inclusion. Passion and determination can to a certain degree prevail over circumstance and lack of opportunity.