Actually, I must say, after looking up records for the most expensive baseball cards ever, it is kind of hard to complain about the cost of certain vintage/ custom guitars (I an at least play a guitar and get joy personally, and maybe even play for others and return the joy, while something like baseball cards just sit there).
If people want to spend $90,000 for a pair of shoes, fine, let them! Imo, it is silly, and for 90k I can swoop up any guitar I want pretty much, play it and enjoy it, then sell it to another collector some day. Just what i'd do with the money though.