How is mining yield calculated?

Take an example of Bitmain second-hand T17+ mining machine
(Supports BTC, BCH, BSV mining and other SHA-256 algorithm based coins, 61T Hashrate, 3.05KW Power)

1. Cost of mining machine: $500
2. Daily electricity fee: 0.04×24=$0.96 (Est. electricity fee: $0.04)
3. Daily Bitcoin profits: 0.00000788 BTC×61=0.00048068 BTC ( 2020-07-16 18:27 Bitcoin mining profits per share per day≈0.00048068 BTC）
4. Daily USD profits: $4.35（2019-04-16 15:02  Take the price of $9068/BTC）
5. Daily net profits: 4.35-0.96=3.39 USD
6. Settlement period: 500/3.39≈147 days

All numbers taken above are based on theoretical calculation for reference only. 

1）Check Bitcoin price at https://www.coinex.com/
2）Check the Est. Bitcoin daily earnings at https://www.viabtc.com/tools/calculator