Really heavy? Well, not as much as a Buick maybe, but pretty damn close. You could probably buy a nice Buick for less than you'd pay for a contra-bass sax!
Look up "The Nuclear Whales" saxophone orchestra. Don Stevens plays a vintage Buffet model Contra Bass. I believe they have some song clips on one of their web pages.
I believe Don uses contra-bass clarinet reeds, and even they are rather difficult to find! It takes a lot of wind to play a sax that big!