Not that Rice-A-Roni is all that expensive to begin with, but Phisch posted what looks like a terrific recipe for making a substitute mix up yourself. You make up three cups’ of the mix at a time, and then you measure out one cup of it when you want to make a batch.
I plan to try it this week. Since the mix only includes dry herbs and seasonings, you make it using broth. That means it should actually taste better than the original, especially if you have some homemade broth or stock. It does mean you have to have broth on hand, but you should anyway — store-bought broth is cheap and shelf-stable until you open it.