Speaking for myself, I don't have a problem buying a bottle for $30-40 or whatever that will last several years (I have yet to buy a full bottle at niche prices). I almost always finish my bottles eventually and replace the ones I like the most. This is a hobby, so researching, testing and exploring the "world" of fragrances is very enjoyable. I am fairly certain that I'll still be interested 5-10 years' time and most likely even longer. If I buy something I don't enjoy, I can always sell it here or ebay.
These are a few of my thoughts on your question.