How can I be more frugal with salt when cooking (dried) pasta?
It's perfectly possible to cook pasta with no salt at all, so you may be able to wean yourself onto a lower salt level, reducing it gradually.

I don't know what, if anything, you're eating with your pasta, so getting that to have more flavour might be an option.

If you're actually eating plain pasta and want it salty but as cheap as possible, the first thing you should do is cook it in as little water as possible, and with a lid. This will also reduce your fuel bills (you can reduce them still further by turning off the heat for a few minutes in the middle of cooking). If you use half as much water as before, you could start by adding half as much salt, so the concentration in the water remains the same. To a first approximation, it's the concentration that matters here.

Even if you're eating absolutely at cheaply as possible already, I'd be very surprised if you could save significant amounts of money by using less salt, and if you can, you need to consider the health implications (I won't go into more detail). Think about how much in total you spend on it, because you can't possibly save more than that.