http://www.go2marine.com/productcenters/heatexchangers/

The exchanger is not necessarily proprietary. It is possible to have something mounted which isn't an OEM gouging price attached.

If you, and everyone else, would not take that crazy pricing strategy. It is ludicrous to have that bit of metal whis is jus a little radiator using more efficient water instead of air. A little premium is one thing. The pricing you have been given is futher mucking.