look 3 months back, 5 USD with 1080ti was normal... than it boosts up to 15...
Who is making $15 per day mining with a gtx 1080ti? the thing is barely making $5 and a gtx 1080 is being sold for $1200, using the calculator + total cost will return your investment in 400 days.
If you are paying 1200 for gtx 1080 the joke is on you. I spent less than that on TWO 1080 gpu's. ROI would be around 5 to 6 months.