That's not unusual for something large and complex. Even video games have multi-year development cycles and double-digit-millions budgets.

$6m in 3 years isn't high at all. Lots of little pre-revenue start-ups have sold for more with many fewer assets than it sounds like this company has. Google's first big round was $25m IIRC, and that was pre-keyword advertising; and by today's standards that's a tiny amount. Good thing its investors didn't panic and pull the plug.