Per Watt Rates in Nevada

[evma582]

I'm looking at adding solar to my house and curious how much I should read into the price/watt differences in the estimates. I've had a couple calls with Tesla and we're discussing a ~7.5kW system and 2 quotes over email for 12.2kW and 13.9kW systems. The emailed quotes come in at $3/watt; Tesla started at $3.55/watt, but countered at $3.41/watt after I sent them the other quotes. Outside of scale (though I don't believe the larger systems would fit), why does Tesla come in that much higher?

13.9 kW system - Panasonic VBHN330SA16 HIT panels, SolarEdge Optimizer inverter
12.2 kW system - Hanwha Q CELLS Q.PEAK DUO BLK-G5 305, SolarEdge Optimizer inverter