$500 for an S7 is way too much at this point. I wouldnt buy one for over say $300 max. If you are buying then in bulk you shouldnt have too much trouble finding a decent price.
He said he had 10k USD, not bitcoin. Where are you going to buy them in bulk for USD?
What does it matter when you can just buy the bitcoin if thats all the seller accepts? Thats the whole point of a fungible currency, you can convert it whenever you want.
Also he just said he has 10k, he didnt mention if it was USD, CAD, RMB, or anything else.
It also doesnt change the fact that S7s are not worth $500 a piece used.