How much a guess post in .gov with high DA can cost?

Hi BHW,

I wan't to sell a new service in Fiverr, Seoclerks... it's to sell guest post in .gov sites.
I really don't have any idea about the price? I see some guys there sell .gov/.edu links for 5$ but they do just links by creating profiles and the majority of them are no-follow.

So how much should I do for guest post?