For a regular business with employees and whatnot, or an AAA studio, I would agree, 200 or 400k is nothing for 7 years. But you're comparing apples and oranges here... game's been on steam not even 2 years, so that should be considered. And again, for indie game developers, it's not a bad revenue. There are very few AVNs that ever hit or will hit even the 1m mark.
He also has (had) the patreon income, which was his primary source of funding until steam release. So if we combine his two patreons while they existed, his SS, his steam sales, add all that for those 7 years, the numbers will instantly look better. Can't say how much better since I don't think his patreon data is available. But by just using the steam numbers and saying that's all he can show for 7 years of work is not fair.