On the big question of 'how do you price Rolleis?', the answer is you google the Antique Cameras website and look on the Rollei page. It's updated a couple of times a year. It lags a bit behind current prices, because collectible models have been rising pretty fast. (A person who makes vintage cameras his business says it's because Chinese collectors have entered the market in such a big way.)
On this particular model, 2.8Cs have a divided reputation. On the positive side, the ones with Xenotars have 10 aperture blades and supposedly produce better bokeh for that reason (though the number of aperture blades isn't the only thing that makes for good bokeh).
On the negative side, first, the viewfinder hood is for sure a nuisance (mine sticks too), and lasted for 1 model. (Marduk, if yours is the same as on an E, then someone was so annoyed that they swapped it out.) Second, many of these cameras were used by professionals and received heavy wear. Rollei's first attempt at a 2.8 (Biometar) flunked out, but this one – its replacement – was a hit. Lots were made but lots died in the trenches of wedding photography and photojournalism.
So weighing both sides, a collector who's a bokeh freak might be delighted to have found a 2.8C that's not too worn. A collector would have Harry Fleenor overhaul it completely, take a couple of pictures and then put it on a shelf – at a loss to photography.
But whatever his enthusiasms, this particular high bidder paid double or triple what the camera was worth. I recently bid halfheartedly on 2.8Cs in comparable condition that went for $625 and $569. The most recent sale was barely over $400 – it wasn't in good shape, but I bought it myself to see if the Xenotar bokeh myth has substance.
Sky-high bidding (as in this instance) is sometimes a psychological quirk and sometimes just a mistake, with bidders unable to differentiate the models and not understanding what's for sale. For example, a late Automat in good but not exceptional condition for over $800, when others sell for about $300? My guess is that someone thought all Rolleis with 3.5 lenses have the same one.
EBay Rollei descriptions and selling prices are so erratic that you can't really tell what to bid or what you'll get for your money. IMO it's a mistake to buy a vintage camera on eBay unless you bid low enough to allow for a complete overhaul. Craigslist is a better way to go. You can pay it a visit, fondle it, shine a light through its lens, put a dummy roll of film through its transport, listen for the length of its shutter speeds, and overall avoid getting scammed.
