> Peta=>Exa equals 1000x so you can get 31x the accuracy in a monte carlo assuming perfect parallelism

True.

> (at 1000x the cost)

Not as true. Summit, the previous machine, hit 148 petaflops (Rmax) at a cost of $325 million. Frontier has already hit 1102 petaflops (Rmax) at a cost of just under $600 million.