They are overestimating themselves quite a bit. The fact that they brought that floaty gameplay dude Nero back was already a letdown, but those deluxe editions are just crazy. Good for a marketing joke but who will be able to buy a bike or 1200$ leather jackets just for fun?
It's not that crazy, really. Collectors often pay high prices for genuine/novel film props and the such. All three of the jacket-editions are closed for sales reservations, and probably all sold quite quickly.
They're not overestimating anything. It's shaping up to be an amazing game, and if I were rich, you bet I'd buy Dante's coat before 99% of the bullshit most people would buy if they could.