In actual use gold toner isn't that expensive. I mix my own from 1% gold chloride, and then the working solution per session. Seven bucks worth is sufficient to tone about ten 20x24 conventional silver prints. You can save money using it more dilute only longer. I don't know about salt prints
specifically, but I'll bet the typical instructions for use of gold toner waste a heck of a lot of it unnecessarily. It's attracted to the silver, and doesn't take all that much.