iStat Menus has a perpetual
(one-time) license which costs $11.99. You do have to pay for major updates (i.e. 6.x to 7.x), but those are at a reduced price, and you are never forced into updating.
You might be getting confused by the Setapp offer directly below it, which is a subscription app service, but you don't need to use it.
Just note that iStat 6.x/7.x licenses are not backwards compatible with iStat 3.x/4.x, so no license that you can buy today from any website/service will work on Lion. You can find a copy of iStat Menus 3.19 along with a trial reset tool on
Macintosh Garden, as it is abandonware. You will have to re-run that tool every 14 days, however it's the only option you have unless you can get Bjango to send you a 3.x license.
Another stats tool that works on Lion is
MenuMeters. Not as customisable as iStat, but it is free.