That does seem steep. Have you tried Novoflex? I'm not 100% certain they do one for your lens but I'd be surprised if they don't. I have Minolta, Olympus and Canon FD Novoflex adapters and all work well. They cost about £100. Failing that I'm pretty sure you'll find an adapter on a certain auction site beginning with "e" for £10 or so. I have several and all work well enough.