they do infact have cheep solar pannels. but the eff. on them is even lower than the good ones which iirc were down to 15%. so 5-10% eff. isnt a problem when you are putting them ontop of your warehouse, but in the back window of your car, you want as much as you can get for that small amount of realestate.
personally, ill be running something like this eventually when i get my aux cooling setup(cools when the car is off in the sun, ie 150F internal tempsl.)