Basically right now the ETH mining rewards is like $1,500,000 daily.

With ETC, ZEC, XMR that figure is almost $2,000,000 daily. So if ETH goes POS, the daily mining reward will only be $500,000 from $2,000,000.

So if you make $4/day now for 2 GPUs, you will make $1/day then. So $0.50/per gpu/ per day.