I hadn't heard of having to buy your way in to a practice, but I have heard of elite practices. What I've read is more that the doctors may charge more than the going rate and may not participate in most insurance plans. And of course they limit their patient numbers and visits per day so they can focus more on each patient.
I don't think setting limits on the number of patients or visits is a bad thing, though only the wealthy will be able to afford it.
But the buy-in fee is ridiculous. I can't imagine he'd be allowed to remain in any negotiated fee networks (like PPOs or HMOs), but I doubt he wants that anyway.
Move on. Perhaps you might want to publicize what he's doing online. There are several doctor ratings websites where you can post this. If he is part of a provider network for your health insurance, then you can report it to them as well. Maybe even get a reporter for your local newspaper to do a feature story on it. Or have John Stossel do his That's Outrageous thing for 20/20 or whatever his TV show is.
Probably it won't harm the doctor. Probably certain people will flow to him. But he'd better be a top-notch physician.