there is nothing wrong even if he ask 1 million USD for his site. if you are interested to buy his site then ask him why price is so high, otherwise i don't see any point to evaluate the value of his site.
anyway normally site sell price goes like this way: monthly revenue x 12 month. e.g. if you make 100USD/M then you can ask for 1200USD but warez has no future so basically these type site price should be much more low.