I already did some crunching of the numbers in another post just for the sake of it, here is a summary of it:
They got $573,939 from Kickstarter.
The game sold 1+ millions copies around the time 1.0 launched, if we use 1 million on point and the average price of $40, since the game went from $30 to $45: would bring us to US$40.000.000.
Using the 30% cut from the platforms (which would be lower, since after a game sell more than US$10 million the percentage can get as low as 20% at least on Steam, that is why I used $40 as the average price and not $37,50) it would bring to around US$ 28.000.000.
There is also some revenue which is more difficult to estimate from the Deluxe edition, battle pass, cosmetic shop and how much the Humble Bundle partner deal was.
So, at the minimum around 29 to 30 million dollars over the last 3 years.