It depends what car it is. They offered £535 for my 944, I guess they weren't interested. They didn't even offer a price for the bay, but they offered £350 for my Vel Satis, and a year later they offered me a fair chunk more. Sadly I'd just sold it for £404. If you want a quick & easy sale for a newish, mainstream car, that's on a par with what you'd get for it as a dealer trade in, they're apparently easy to deal with. And certainly a lot less stressful than dealing with the funktards & window lickers who inhabit ebay & gumtree.
