I see it coming: "Pay five bucks to get your message delivered in just ten minutes!"
There is zero economic incentive to pay and stay in that frame, and subsequently none for the company to adopt that approach.
It is all the legends of crap that gets send because email isn't even a penny a letter I object to.
Even physical mail is too cheap; advertisement leaflets and "free" catalogues are like 90% of my total mail volume (after putting "do not deliver advertisements to this mailbox" stickers on everything), a worse quota than with email (after setting up basic spam filters).