Dan, I don't think that anyone buys these CDs/DVDs at such ridiculously high prices. I don't even know why they put them up for sale. Maybe some wealthy Russian or Arab, fan of MK will buy it!!!
It is a total rip off, even for them. If you wait long enough you will find everything at the affordable price you were willing to pay. Of course seeing the first edition of BiA longbox, was a thrill and I was willing to pay for it up to 50$. But it went over 100$!
My guess for the ones with the overpriced items (200-700 dollars) is that they are re-sellers, actually not having in their possession the object, but with better means to advertise it and sell it. When they get the sale(remember they are getting paid in advance), they find one such copy at lower price (or have already located it) or cancel the order if they can't find it. I don't know if ebay allows such tactics, but I have seen it happen at Alibris.com.