The cost of the Mueller Investigation is NOT just thee $50mm dollars, it's the cost to the 2,800 people who were subpoenaed and had to hirer expensive lawyers to answer.
A minimum cost to answer a subpoena from Mueller would be $20k, but I'm sure most spent multiples of that to avoid perjury traps etc. So the cost of 2,800 subpoenas would be between $60mm and several hundred million.
After 22 months, 19 attorneys and from over a hundred million to perhaps 1/3 of a billion would be the true scale/cost of the investigation.
Isn't that enough? What about the lost energy of the nation siphoned off for this witch hunt?