> Such an attack doesn't exist.

As far as we know.

> Any such attack would also become feasible with twice the budget.

Assuming that the attack yields to parallel computing and scales linearly with more cpu/cores, because linear programming is bound to current compute capabilities and then theoretical limits like Bremermann's limit and Margolus–Levitin theorem.

Assuming the parallelism of an algorithm that you know nothing about is beyond foolish.