Well, these are the typical reasons a person buys an account for:-
1) To rent Signature space
2) to use the account's rating to offer some other service or sell some stuff
3) to scam
And all of these require posts in English. I am not saying they are not valuable posts, but for buyers they might not be worth it.
And if we are putting something to find out value of the account, it must be somewhat near the valve they might be sold for. Otherwise its just a play thing... Or just for curiosity...
-troy112

P.S. I am not trying to offend any language or anything like that ...