Nothing is more idiotic than bidding up an item at auction, either online or offline, and making the assumption that you can return the item for a full refund. Most government auctions do not allow returns of any kind, with the single exception being if the item is misrepresented. Government auctions are typically very thorough in their representation of the items, so the chance of being able to bring something back for that reason is extremely small.

Almost all auctions, online and offline, have restrictions of some kind on returns, and this is where the transaction can be vastly different than the retail environment, which strives to make that process easy, hassle-free, and with no penalty financially.

Online auctions are a different animal altogether. They represent a wholesale purchasing environment, not a retail one. You need to factor this into your bidding. Even if the auctions accept returns, there is almost 100% certainty that they will not pay for the return shipping charges.

Be careful about eBay sellers who promise 100% money back guarantee as well. While some of them are legitimate, keep in mind that eBay will not force anyone to give you money back. Again feedback ratings are key, so read them carefully.