I use ebay a lot. Never had any problems with it or any sellers. I am primarily a buyer but I have sold things in the long distant past.
Fakes are usually pretty easy to spot. If not, most sellers make a note that it is a fake and if they don't, most items fall under ebay's guarantee.
Sometimes something is slightly worse than expected but usually things are better. Photos are key. I don't buy anything with lousy photos and can't for the life of me figure out why someone posts them other than to be deceptive.
I've bought quite a few bayonets, books, slings, parts, etc. I shop prices beforehand so I don't go overboard with bidding which is easy to do. I've found most items, with the exception of rarer books, come up again pretty quickly so I don't settle for either a too poor example or a too high price.
Always ensure you check postage before bidding. There are a few people that charge very high prices for shipping which counters their low bid start price.
You also need to positively identify things before bidding. Don't go by what the seller tells you it is. If YOU are not sure, ask questions, research it, etc. There are sellers especially of bayonets that simply don't know what they have and since the writing on it looks
German
, it's a German bayonet whether it is or isn't.