Trolls and bots

I don't have a twitter account and don't do much on FB other than keep track of a few relatives and friends.

So maybe the answer to this question is obvious to others.

What is to stop a US entity from creating its own troll/bot army with its own messages directed to its target market. After all, how much did this Russian effort cost? Hundreds of thousands? Millions? Surely there's a liberal billionaire out there willing to counter mercer, koch, other RW extremists, and Russian/Macedonian/etc. trolls.