"per post" is correct and usable in written English.
You can use it to refer to something that is sent or delivered via post or mail. For example, "Our company offers payments per post."
In Pay Per Post's case, the simplest explanation would be that most VCs want to keep their hands clean.
"At the moment you're looking at 10-20 postpost.
Mr. Reynolds rarely goes beyond two or three lines per post.
To reduce the abusive comments, the system charged 25 cents per post.
— could face huge fines ("up to $11,000 per post," Mashable.com asserted) for inadequate disclosure.
The chemistry of Baristanet's topics, tone and length prompts reader contributions at an impressive clip, often dozens per post.
In December added per-post privacy.
Now, before you cry Pay-Per-Post read on and let's figure this thing out.
After that it will be a pay-per-post model with discounts for volume.
You'll be able to disable comments on a per-post basis along with other controls.
A few independent games journalists, for example, have created campaigns that charge on a per-post basis.
