My friend's dad recently started mining BTC with his gaming PC while he's not using it. As far as I can see, this kind of mining is not profitable anymore. He gets 40 Mh/s on average and apparently has made about $10 so far. I tried busting out my old Block Erupter USB miner which gets about 250 Mh/s and it hasn't made anywhere near $1. I'm wondering if he's just messing with me or if I'm missing something important. He could be mistaken about what coin he's mining but I'm pretty sure it's BTC.
Mining Bitcoin at 40 MH/s is not profitable.
Unless you get free electricity and consider 4 cents a year profit, there is no point mining Bitcoin with that hash rate.
Does your friend's dad have $10 in Bitcoin from mining with that hash rate? Simply put, no. Your friend's dad could have, however, been mining a different cryptocurrency without knowing. 40 MH/s mining Ethereum produces $3 a day.