You might try making several tables (or piles or baskets) with smaller cuts for say $2 each, and larger cuts (perhaps 2yards-4yards at $6-8 each) and then full yardage pieces of 5yards or more for $12-15 and just post signs above. You can always take a quick measure to keep everyone honest!
I would contact any local quilt guilds and give them an opportunity to do a preview sale the day or so before, you might just not have to fool with any of it when they finish!