You can use use visual quantities instead of numbers. Then when it comes to spending resources you could make it so resources are gradually spent on a thing until it's cost is fulfilled instead of instant spending which requires a specific amount of resources (like with Supreme Commander, Settlers IV and Rimworld), that allows you to be a bit more vague with larger numbers since counting individual resources would become tricky unless you have some kind of compression.
You also have the option of using segmented bars if you have resource caps.
You also can ask yourself if you need to have large quantities of resources and whether you can design the game with lower resource counts.