I believe it is because they are no longer being produced.
If you look under their "E.A.G.L.E." page:
The Barrel Assembly offered is 9 inches long with a 12 inch option. A nine inch barrel has been used with success on the
Diemaco 40mm M-203A1 Grenade Launcher. The nine-inch barrel has been tested extensively by the Canadian Forces and Diemaco with various types of practice and HE rounds.
There is also a big "D" stamped on the side too.
Most guys I know, and myself included, do not like the mounting mechanism. although reliability and accuracy are excellent. Probably why the Dutch and Brits use AG36 on their C7/C8s instead.