We provide no hidden calculations or whatever else. BTC price above was just taken as an example and instead of 100k$ I could write 1$, but who wants to believe that BTC price will be 1$?
The forecasted BTC price on the web calculator is based on average BTC price fluctuations for the period from 2017-12 to 2018-05. You can always switch to the market price if you like.
I don't know how did you calculate 23 USD loss, but i know for sure, if the BTC price will continuesly fall in future none mining company could give you any positive value of profit. So everything depends on BTC price and network difficulty.