- assuming on average 2016 blocks per two weeks --> (2016 times 26) divided by 12 equals 4368 blocks per month on average
Such a miner would need a mining farm of ~865 (121,108 divided by 4368) of such devices and as cheap as possible access to power delivery of at minimum 2.6 MWh for the ASICs alone (not accounting for power losses of distributing the power internally, operating the mining farm facility, cooling, ...).
He would need the same if he would be mining in a pool, yours till need the same thing, asics, power, land, technicians, there is no difference in it, the only difference would be like for for a farm to sell it's products to a chain of grocery stores or do it themselves, all the manufacturing process is the same.
That's serious business and investment for one block per month on average and I'm already assuming ideal operating conditions.
Let's replace your 865 S19 with 605 S21, that would be 2.4 mils but you're looking at 7.364 BTC (last block revenue per month)
Now you could get that hashrate and mine at Viabtc and get 0.00000198 BTC per th/s so 0.23979384 BTC a day, 7.1938152 a month!
See? No real difference in revenue, it's just that it won't be a daily payout and you risk both getting a low block fee but also hit the jackpot.
You can make that a block every two months or a block every one week, the revenue and investment model is the same!