It's actually closer to 6 million after Steam's 30%. However, the amount they made is actually beside the point.

You bought the game for $18 to $25, knowing it was in Early Access, on the notion that 2 indie developers will do their thing, regardless of the amount they made, that it might take anywhere from 3 years to forever. The amount of money they made is irrelevant, because it has nothing to do with you. In other words, you buying a loaf of bread for $3 doesn't have authority over Dempster's Bakery on how they choose to run their multi million dollar business.

If you think supporting Early Access isn't a risk, but rather, you being in a position of authority to dictate what the developers should or should not do, then you're naive at best. Don't like the pace the developers are outputting updates? Then perhaps take this as a learning tool that IronGate and Early Access development isn't for you. In the future, don't buy Early Access.

Personally, I'm 90% fine with the way things has progressed. All 9 of my players are fine with the game's development. A lot of people are fine as well. I am not saying your opinion doesn't count. I am saying your opinion that they owe you something because they made $8 ($6 m) million doesn't give you authority over their development process. That is all.