It's a mistake to think in terms of USD profit.
The profit is really valued in the currency that you pay your electricity bill in. But since they are exchangable, it doesn't really matter.
Furthermore, even if you don't care for Bitcoins, no one is obligated to sell at the current market prices, that's actually the stupidest way to go.
So who is buying above current market prices?
At least for the time being, I think most people/companies who approach mining as business need to exchange the generated coins to another currency in order to pay the bills.
He is talking of mining and holding, hoping for the price to go up. That is a valid strategy, but if you are counting on the price going up, you can often make more if you _buy_ and hold instead of _mine_ and hold. With rising difficulty, many cards will not ever make as many bitcoins as you could have bought with equivalent funds at the time. This is particularly true is you time your buy well, like the $11 dip yesterday.