What’s the maximum amount of money saved by minimizing line loss?

When electric power is distributed through the national grid, the nominal voltages are typically: 345, 138, 34.5, and 12.47kv. When voltages are higher then their typical nominal level, power can be saved from a reduction of line loss. Power saved = money saved. My Question: When increasing the voltage or conductor diameter from the standards today, what’s the maximum amount of money saved from minimizing line loss? Is it enough to be worth the investment of the cost of replacing higher rated equipment?