It is a great pity that ebay do not take more action when people refuse to sell items to you.I have had this happen twice when a collection has not realised what a seller wanted for it.Ebay say that you enter into a legal contract when you agree to sell or buy at a price but have no power to enforce this.
Particulaly new Sellers either put a reserve on your items (which can put people off bidding).Or better still put a starting bid which is the lowest amount you want to sell the items for then you will not have trouble.
You risk bad feedback and cause an awful amount of time waisting if you do not follow these guidelines never mind bad feeling all round.
Also many sellers refuse to sell to newbees because of this no wonder.Don't agree to buy then refuse to pay or worse still string some one along then still refuse to pay in the end. Most sellers are doing this as a hobby and make little profit as it is they do not have the time to waste dealing with these problems.
If more people considered the consequences of their actions ebay would be a really nice place to be.