It depends on the computer.
An average 3-year old computer (with a Core i7-3770S processor and an AMD R9 270 graphics card) shows a profitability of about $30 per month. A computer with a Nvidia GTX1070 video card can bring up to $ 45 US per month, and with two AMD R9 390 - about $110 US per month.
Profitability depends on the rates of Crypto-currency and can both grow and decrease.
