Agreed, this doesn't seem overly expensive by any means. But worth noting this is just one developer's cost. Doesn't including licensing/support costs for Domino/Notes itself, hardware to run it on, sysadmins for the servers.

(And I don't know what platform they're using, but it does run on all of IBM's OSes: AIX, i5 (i.e. OS/400), and z/OS. Wouldn't be surprised...)