There was a website that used some sort of algorithm (I think) to value the BTC price of a certain account.

I think no algorithm would be enough to decide the price, it all comes down to the market. I would personally never sell my account for less than 1 BTC. I spent so much time in this forum learning and posting, I reached Hero Member... I value my account too much, so 1 BTC minimum. I think that is the average market price for Hero Member accounts with real posting and not total gibberish usually in some foreign language/offtopic section spam.