They have every right to ask you to pay $10 if you want it back. Consider this: you donated the quilt to the organization and if it does not sell, you have first refusal to purchase it for half the opening bid price or pay nothing and donate it to another charity of your choice. Either way, you can claim the cost of making it as a charitable contribution. They could simply keep it for next years auction if they wanted to because once you donate it to them, it is theirs to do with as they wish. They are not being the least bit unfair in my opinion.