It’s surprisingly cost efficient to buy the Presidency, if you don’t mind being it obvious after the fact.
Forget about bombarding the airwaves with ads, by taking over a political party, or any crap like that. States take the popular vote, then the winning side chooses electors to go to the capital and vote on the next President. There’s no law that says they have to vote for the will of the people. Buy off 270 electors to vote for you and you can be President.
Although, to be fair, it’s even more cost efficient to just buy a President.