I know some people will disagree with this, but I've come to the conclusion that eBay is not a good platform for amateur sellers who list an item once in awhile. eBay is not a classified ad service. From a seller's perspective, it's quite complicated, and you have to stay on top of it and understand how everything works, or you can really shoot yourself in the foot.
If you're a very small-time seller who just wants to move the occasional item, I would honestly recommend using other platforms that are geared toward local in-person sales, where the potential buyer will simply contact you and work out a deal. I see numerous faulty eBay listings posted by new sellers, where I know somebody is going to end up very unhappy when that listing sells, and it's just a question of whether it's the seller or the buyer.
The cardinal rule to keep in mind is that eBay sales are a binding contract. If you have a listing posted at a given price (INCLUDING automatically-generated shipping quotes!) and a buyer clicks Buy It Now and completes payment, you are obligated to deliver the item to that buyer at that price, period. Yes, there are ways out such as cancellation and refund, but all of those count against you in some way. Once the item is sold, the only clear path for the seller is to get that item to the buyer. It does not matter if you accidentally listed it twice or you screwed up the shipping settings.
This is why you have to be careful and understand what you're doing when listing items on eBay. I think every seller here has at some point screwed up, so we all know the feeling, but generally it's seller error and not some bizarre glitch that listed your item twice or misstated the weight and dimensions for shipping. Not saying it can't happen, but it would be very rare for something like that to happen. If these things were happening all the time for no reason, the big sellers would go bankrupt and nobody would be listing here.
