Cheapest price for this manufacturer, model, and watt size with thermostat: Natural Light Roof Mounted Attic Fan 60 Watt With Thermostat [infinigi.com]
Not the cheapest brand but the quality (based on reviews) & 25 year warranty makes up for it (in biz since 1999).
The solar panel comes with a 15' ft wire so it can be installed in direct sunlight remotely away from the fan.
Natural Light Energy System's customer service & management were very responsive and informative via phone.
Solar Tax Credit offer has expired
Shipping is extra.
Tax: California based retailer. Texas was tax free for me.
Details from the manufacturer:
I do not work for either of the companies (manufacturer or retailer). I am just helping others out based upon my research.