If someone knowing about how it's difficult to rank up a forum account with trusted rating, he would definitely conclude that the price is so cheap compared to its really value. Yes it's so cheap imo and i have my reasons saying this :
1. A legendary account can earn that amount in less than a year by just joining signature campaigns.
2. I remember there was a website in which you can check the average price of a specific bitcointalk account. And i remember that a trusted legendary account may reach more than 5000$.
By searching the web, you may find many people claiming to sell forum accounts. Be sure that old ranked accounts couldn't be sold unless they are hacked from their original owners.