Seller says my winning bid was too low

[limitednames]

So I bid on an item with no reserve and won it (there were several others I was bidding against).

After the auction was over, the seller says that my bid was too low and the item is worth more than I bid, so he cancelled the transaction.

I wrote back and told him that this was really  not how an auction works, and he should have used a reserve price to protect himself if this was a concern.

Never heard back from him.

Is this really a violation of terms, or can a seller just refuse to sell if he feels he didnt get enough? Also, if this is an acceptable practice, than why would anyone pay the extra fee for setting a reserve price ?

Interested in your opinions

Thanks