Kimbo, it's probably a little like paintings - you can't search out every artist that may be worth something a little extra. A lot of the time they have to be up there for people to see them and if they are 'up there' but hidden in a crowd then it's less likely people will spot them and the seller is less likely to get the best price. Would you sell something today for £20, that maybe you would get £400 for if you could get it the right venue.
Leads me to ask ... why did I post in 'Quick Reply...'