Well personally I have 7 - Nvidia 1080's and 1 - Nvidia 1080Ti.  Using Multipoolminer on ahashpool.com I pull in about $8-10 per 1080 and about $12-14 on my 1080Ti.

Power usage I pay .13/kWh and end up paying about $160/month for the power to run them 24/7.  So net I'm bringing in about $1900/mo right now.