First, as others have mentioned, they have a monopolistic marketplace where they require one to use their own Paypal for transactions. The combined fee's for selling on ebay + Paypal now are 10% of the final sold amount + the shipping amount. Where margins are slim as it is and things are already selling well below their value at times because of so many other competing auctions, the fee's make it not worth it in many cases. They are making a boatload in fees and I'm tired of it. I just sold $400 golf clubs and had to give them $42? Ebay provides value as the market is so large. I had those clubs on Craigslist for TWO months and not even a inquiry at that price. Ebay got sold in 7 day auction. But to pay 10% for everything is too greedy imo. They have NO competition.
Second, ebay has become a haven for scammers and overrun with them to point I am leery of purchasing anything like electronics, phones, etc on there. Software..forget it! DO NOT buy any licensed software from ebay no matter how good buyer feedback. Even if it claims new/sealed. The pirates have gotten too good. I'd venture to say 99% of software on there now is either a)counterfeit from get go or b)legit but "used" and/or illegal Volume Licenses. The problem is key will work when you get it but fail 5 months from now or when you need to reinstall. I've been victim of this two times now and NO more will I buy software off ebay. When it does fail, it is long enough you have zero recourse. Ebay you can't even file a claim as they give you only like 14 days after purchase. A pirate knows this and gets keys from a keygen. I had 8 legit looking MS Office licenses in sealed retail boxes register then 4 months later started to fail. Called Microsoft and they told me I had registered them too many times and they are now flagged. Huh? I only installed them ONCE. Credit card company didn't even help as it was past the time limit for a case. So basically the seller sold many of the same key and whoever bought from him, who knows how many of us, they are all worthless. Really upsets me that ebay allows ANY software even on there. They clearly know that this must be going on. I tried to inform them of the practice but couldn't even find a contact to let know. They don't care as they are making their fees! Tons of them from software. Their only concern is a small webpage to help identify counterfeit. From now on, I will only buy hard items that can't be counterfeited or scammed easily, like golf clubs.
Third, as this story is about, ebay is WAY to buyer-centric and I too was once bitten by similar story as topic starter. Not as blatantly bad as the OP or that amount of money, but bad enough I was pissed. Eventually also got someone from ebay on the phone and as similar was brushed off and there was no pleading my case. End of story, refund the money. It cost me out of my own pocket by time it was returned and settled.