I have noticed that phenomenon. When you buy from a dealer, you get a good price. When you buy from a collector, it's like a sacrifice to the gods. The 70 grade coin is advertised for $100,000. I bet that guy bought the coin for under $5000, if he got it from a dealer (he might have gotten lucky in his own submission).
The really scary thing is that somebody out there might actually pay such a huge price. In a country as big as China, with lots of rich people spending stupid money on stupid things, it would not be surprising if it actually sold. I know I want it, and I can't afford it :)