The smartest way I have found to deal with situations like that is to create a separate website and have your listings all point to one place. For example lets say you create a listing on ebay. Then you make all your info point to a free website you created somewhere. I use myownfreeweb.com when I need a quick website. This way you don't have to keep reposting everything all over the place, and you can avoid having to pay anything to ebay since you directed the sale out of ebay. I know they tell you not to do that so they can make money off of you, but you can link to an outside site and later just let the ebay ad expire with nothing sold. You can also use it for Craigslist and all sorts of other online sites that limit your description or posting abilities.
There's other ways to sell your car if you don't agree with the fees, and the fees are listed on their page
There are hundreds if not thousands of people unhappy with eBay! I say that as someone with a 100% positive ebay feedback and the only answer I can see is that a couple of dozen people get together and between them/us make something even better! It's not all that difficult with the right people geting together with complimentary skills and the right branding, SEO coding, legal rep and a few other things. The hard part is getting a couple of dozen people together to pull it off who wouldn't backstab each other and who are not in it just for the money but want to offer something better and different! The eBay model in many cases is a good starting point and model to from, in other regards as you say it needs a better / different approach.
I think it'd take more then people power but funding if you want to try to take ebay out. They have been around for so long with a massive amount of users worldwide. And there's alot of places that offer this service on top of that so it's not like ebay is the only one. They do charge a tax on everything I agree and have sold plenty of items and sometimes do feel ripped off, but feel safer selling there then on craigslist unless the person is local but will most likely sell for less anyways. I just say good luck in trying to out do ebay.
Personally I always research any fees I might have to pay before listing anything I want to sell on any type of site. It tends to avoid this sort of problem. Still, lesson learnt and all's well that ends well.