But it doesn’t pay for itself is the problem - and I’m pointing out that the prior poster was pointing to a fundamental reason why that is not likely to change if the input fuel is cheap.

If the input is expensive, then the economics change and it’s more worthwhile to pay more in equipment to get more out of the input.

I bet someone has a really detailed set of calculations that would tell you exactly when that line is crossed. But I doubt they are hanging out here.