I think No Man’s Sky is also in the same boat.
I mean games which keep releasing further content over long periods without charging extra for it. Surely the amount of new sales eventually dwindles considerably. Is the cost of new content once you have the core game this low or…?
Path of exile is another example. Many many years of new content, base game is free. You can buy increased stash size, which, while difficult, isn’t necessary, but massive QOL. You can also buy cosmetics.
Someone like me likes to support them for the hours I play, so when they release new context every 3-4 months and new leagues start, I usually buy something from them.