I don't know how you make your calculations but they don't sound right. They can be right only if you have free electricity and by 12 dollars daily as cost you take your initial investment at the price you bought the rigs or mining devices.
Nowadays conditions are not worthy anymore, even at the 0.09 dollars/kilowatt energy cost. My colleagues turned their rigs off because one rig with 6 Rx 580 was making 0.0036 bitcoin weekly and 0.015 almost monthly, that is only about 90-92 dollars, they paid energy for a rig 80 dollars so for just 12 dollars monthly profit was not a good idea to keep the rigs on, not worthy.
This is the big picture in Gpu mining nowadays.
Easy to spot problem in here. They need better bios mod... good timings and undervolting. Maybe also mine different coin.
These are the only possible factors but having a daily of $30 minus the expense of $12 which leads to $18 profit everyday will really be hard to believe.
The only thing comes to my mind is about mining a different coin when we do talk on such profitability.
I don't know I've been mining for about 5 years now and mining has died at least 3 times, see some of use are here not to make a quick buck but to push the chains because we believe in cryptocurrency
Miners aim for its sole purpose and foreseeing its potential vs for those miners who are just targeting profitability - these are 2 types of miners actually.