In 2015, one AMD Radeon R9 280 video card gave about 6 Ethereum coins per day. Even if I were to sell coins now, it would be millions of dollars. But then no one understood the value of these coins and miners sold them for a few tens of cents or less.
Mid 2017 a R9 280 make 0.2 eth per month...
Yeah the r9 280x was a killer GPU for Ethereum. I remember back in late 2015 and early 2016, you basically made 1 ETH per 280x per day. Keep in mind ETH was like $1-5 or so back then.
However difficulty was low, DAG was low, nobody was mining it because crypto seemed dead at the time. Those who believed in it made it out big.
Especially if they also kept their ETC which happened after the DAO hack. ETC also had some great runs in price.