OP, I suggest to add more details to your post. How many posts a month you usually make on average? In which forum sections you're posting most?
But don't expect to get many offers. I see that even some users with great reputation and posting quality are strugglint to rent their signature.
Why not? It's free market and everyone can set their own prices. $80/month is still better than nothing. Offcourse, best posters with lot of merits earned wouldn't be interested in such offer.