For a simple circuit / thiristor such as the icecaps use, they sure soak the heck out of your wallet.....The fans in all reality are not any better than most offered for a fraction of the cost, and the electronic circuits is dirt cheap to buy......Truthfully all four are not worth what one pays for one of them. I paid 82 cents each for needed electronic component, and it took maybe 10 minutes of my time to solder in. I paid less than $3 each for my 4" fans.......from surpluscenter dot com Icecap may be top line stuff but the name itself is not worth the additonal price espeically for such an item as temp controlled fans.