Would you pay 500$ for a Nick Cave concert poster? Some people apparently do and, according to this Guardian article, they pay even more for other posters of contemporary rock acts:

Now contemporary posters are fetching silly sums, too. A Citizen Kane-style poster for a White Stripes’ 2003 gig by Chicago artist Rob Jones (who does most of the band’s artwork) sold on the night for £15, but fetched £1,600 on eBay in 2008. “Each [poster] was done in a limited edition of 333, for every concert, and there won’t be any more,” explains Jody Goodall, director of Manchester’s Richard Goodall gallery.