...as such Roi can be high...
Well, I hope you know that's not true. Even with the "zero" running costs at 5% difficulty increase per retargetting interval (which is very conservative) you will not make ROI in less than 12 months. With the more realistic 8% it will make ROI in 3 years.
Sorry, don't mean to troll, just stating facts. You can do the maths yourself.