It's not impossible to get your foot in the enterprise door, I've built several solutions for one particular client.
If you've got a contact who trusts you then you could certainly pitch solutions to them, and the prices you can charge are a lot higher.
Do you want to work in an environment where your target browser is IE6 though (not even joking).
also, the sort of enterprise you speak of would certainly not be purchasing software like these - they'd stick with the trusted and known big name vendors. As they say, nobody ever got fired for using IBM (or microsoft).