That solar system, while tracking helps produce about 25% more power than a non-tracking flat mounted panel, still is only going to make about 85 - 100 amp hours per day.
My 415 watt solar system will also make 120 amp hours per day, and that solar system is not that impressive. Mine are flat mounted, and I no longer take time to tilt them. When I would park either northbound or southbound, I could tilt the larger panels, and expect to get about 150 AH daily.
Now days it is less expensive to buy an additional pair of 150 watt solar panels ($350) than it is to install a tracking system on a 300 watt solar system (trackers cost about $2- $8 per rated watt in the 300 watt size range for home based systems that are mounted into a cement pole in the ground. I have no idea what that guy spent in hours and materials, as well as some sort of tracking system to control the motors that move the system, but I would not be surprised at $500. Under $250 would surprise me.
Fred.