So I have 1 dirt miner, pulling in 0.00004 Satoshi/s. A second one costs 152 Satoshi, making my total Satoshi/s 0.00008.

If I upgrade the 1 miner I have to level 2, it will also pull 0.00008 Satoshi/s, but it will cost me 250 Satoshi to upgrade.

With this logic, why would I ever upgrade a dirt miner, when I can just buy another one cheaper?