As Max said, people in hidden don't show for Steam community stats. Steamspy does report 600k sales though, so I don't doubt them on it.
If I had to guess ( and hey, isn't that what this is ), EA launch was the majority of their sales, and probably accounted for 300-400k total sales over the first few months. It had a very big launch after all. It's probably been a trickle since then, and let's say 100k-200k for 1.0 launch.
That's still almost 5mil in total rev off launch. They dropped most of the dev team a year ago since I'm guessing the contracts ran out and they didn't renew. At this point it's what, DC, Sam, Tibor, and like 2-3 actual devs? 4-6 people total. Even if they only have the 1.0 cash reserves left, they still have enough to make some DLC and have decent enough cushion for next steps.
The pushyness around launch is them probably bad marketing/awkwardness more then it is an actual need for cashflow. Unless they really want to push for growth to try and transition into a Subverse 2 or something and want to see how big they can get the nest egg.