M/T Radiators cost more than A/T?

I would call them on it, it's bullshit. so they don't sell as many manual ones as auto, does not cost them any more. and if U buy the auto one U do not need to plug anything. I have an auto unit in my 4 gear car, bought it that way
You obviously don't understand supply and demand very well. Lower demand means less stuff bought/built in bulk. Prime example, see chebbie small block part prices compared to mopar stuff....