This is a great diagnosis - thank you. You're exactly right: the v1.1 soil-hardness mechanic divides dig power by depth resistance, so at deeper strata each auto-dig tool only adds fractions of a meter and the purchases stop feeling meaningful (which is what w8gr was hitting). That's a side-effect of the rebalance I need to undo - hardness should still slow you down without making auto-dig upgrades feel inert. Reworking the curve so buying a tool gives a real, visible m/s increase at any depth. Really appreciate you pinpointing the actual mechanic - that saves me a lot of digging.