True, but I have used the others and GoogleMaps has much higher resolution at my flying sites. I skimmed and recall the figure $200 per year. I bet we could get funding for that if it would be the easiest code change, allow us to keep using hi-res maps, and assuming we are a small enough community to fit a plan this inexpensive.
I think I recall that TauLabs / dRonin has some similar purchased key.