Yeah I noticed it.
At first there were some decent bids in the 300-400 euros area, then someone massively overbid everyone else with 500 and later 550. A few days later those bids were revoked, as well as another guy’s who also bid high and had made me increase my bid earlier, so obviously they were not seriously interested and all they did was artificially drive up the price. (There’s something to be said for eBay’s strict bid-and-you-buy policy…)
Then the seller pulled the auction, probably disappointed he wouldn’t get the 550 euros he thought he would be getting, and relisted it for 550 euros, then a few hours later changed it to 650 cause hey, why not ask for even more. Despite the fact that those people were clearly not prepared to pay that much or it would have been sold already, apparently he now thinks that’s a proper price. I guess the high bids made him get euro signs in his eyes.
Maybe if it’s boxed and in perfect condition, without yellowed keys, and you put it on eBay. One did sell there last month for around that much, though IMO that was also way over the top (last-minute sniping bids), the seller got a good deal there 
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Glad I bought my boxed Turbo-R ST with 230V and 512kB for 400 euro some time ago
He means 300 