I was in a guild that did that. We simplified the pricing by wrapping each piece in a piece of yarn, the color corresponding to the approximate size of the piece. Then anything with yellow yarn was one price, red was another.
It was simpler than putting price tags on each item and made it possible for us to reduce prices at the end of the day by just changing the dollar amount corresponding to each color.
My current guild guild makes up baskets of the donated items and raffles them during a meeting. We buy tickets and place them in bags next to each basket full of quilting goodies, and then a ticket is picked from each bag.