While it may not be a new market, I’m pretty sure the sales numbers for MSFS are unique in the past decade, and the whole online / integrated economy of it; all is new.
Over 1M sales in september already (no clue what they’re up to by now), $2.6B in hardware sales expected in the coming 3 years linked to MSFS
Microsoft Flight Simulator 2020 to generate $2.6B in hardware sales | Windows Central
There are already massive shortages of flight sticks, yokes, HOTAS sets and rudder pedals. Doubt any sim release had this effect before.
Not exact science, but it shows the numbers that are possible in economies of scale.
So yes, I am saying the market has shifted immensely, and third party developers will have to adapt to be as successful as they can be.
Can they survive by selling airports for 15 dollars? sure. Could they be even more successful by selling them for $3 with a market this size (especially when there’s enthusiasts providing free content as well as you stated yourself)? Most likely yes. It’s up to them to find out.