this question has already been asked here https://bitcointalksearch.org/topic/cost-of-bitcointalk-accounts-1029508
use the search function next time
use the search function next time
He didn't even have to use the search function. I believe that the post was on the first page. Probably just trying to boost up post count.
To answer your question in a simple answer, the cost of accounts greatly varies depending on the current active signature campaigns out there and their pay rates.
Full member accounts seem to go for 0.05 - 0.15 BTC, Senior 0.3 - 0.5 BTC, Hero 0.5 - 1 + BTC. Trust rating, activity, and post quality are also factors.
You're going to get a thousand different answers here. 
