Some interesting comments.
Back in the day, I vaguely recall that several record companies' PR departments seemed to think that producing large but limited edition promo box sets would impress journalists and thereby help sell their artists' output. As for collectability, such box sets do offer very little to a fan in terms of content but, nevertheless, are desirable to some - and it only takes one person to buy. if two people desire it and have deep pockets, the price could go up and up.
I agree about Gilbert and George. I have never understood the attraction of their works but it is all a matter of taste. I would love to own something from the 1960s by Bridget Riley but could never afford it, while I couldn't pay enough to persuade others to stick one of her works on the wall. Ditto Roy Lichtenstein.
As for Colouche's humour, it is lost on me, I'm afraid. It seems more a statement of the obvious but I guess I'm missing the point.