I'm new to mining and I'm trying to understand this.  

So using that assumption in "https://www.coinwarz.com/calculators/dash-mining-calculator/" and halving the current block reward

Difficult: 10000083.13284920
Block Reward: 0.90147602

Product: X11 - 15GH/s
Hardware Costs (USD): 1600 incl PSU and shipping
Power Cost ($/kWh): $0.12
Power (Watts): 1200

Earning:
Annually:  9.92861277 DASH coins
Annual Profit (in USD) after pool fees plus electric:    $2,267.83
After Hardware costs: $667.83 a year.  

So a return given the assumptions above for a year is $667.83.  

And I just got two of these machines from the last Nov batch....smh...my payback period is going to be non-existent