Every year I go to the Mennonite Relief Sale in our area and I'm amazed how broad a range the quilts sell for. I've seen heirloom quality quilts go for as little as $500 and others while nice will go for over $1000! Before the economy collapsed they would go for 3 or 4 times those amounts.
But a couple of things to keep in mind at auctions, people are there looking for a bargain and the quilt is only worth as much as someone is willing to pay for it.