Your share of the network is the whole game
The network mints a fixed number of coins per block, and your miner earns in proportion to its share of the total hashrate. Your hashrate in TH/s divided by the network hashrate in TH/s is your slice, and that slice times the block reward times the blocks a day is your expected coins.
Nothing about the machine itself matters until it is expressed as a share - a bigger network means a smaller slice for the same machine, which is why difficulty rising is the same as your earnings falling.