I have found most of the sites are copies sold over and over again with a different domain name. I have has much better luck purchasing sites via webmaster forums like DigitalPoint. If you do purchase a site claiming to have revenue ask for screen-shots or ask if they can install your tracking code on the site so you can verify claims.
We have trademe and sella in NZ instead of Ebay (ebay failed because they used US currency when they launched here- which was annoying). Sites are way cheaper here, and often more advanced technically.
a lot of them are turn key websites that the webmaster has set up 10 of them and is selling them. not very unique.
It takes a long, long time to search eBay and find anything worth buying. Almost all the sites are junk. It's probably as lucrative as going on a hike and spending the day panning for gold. You have a slight chance of finding something, but most likely, you'll search for hours/days/weeks and not come up with anything.
Listen now. I have over 4 coaching clients that bought websites through ebay and the sites were sandboxed. Those sites ARE not good. I eventually helped them get it out and start earning money again but I dont suggest ebay. Flippa is the best but more expensive.
I do not think it would be a good idea to get sites on ebay, as mentioned in some posts above, some of them are resold and you never know if you are genuinely getting something another person already has. I have no idea how they keep track of that. Im more comfortable buying from a specialized company.
My advice would be check the feedbacks and paypal is a must. I seen some good services on ebay and used a few which went ok but always make sure to check seller feedbacks to see what other people are saying.
Instead of buying websites from e-bay, its better to buy domain separately and outsource design to some freelancer!