I understand where you are coming from and yes it's a very niche market. Your reply makes a lot of sense to me and yeah I can see how the DLC price can be justified due to all of that. Very nice comparison to X-Plane there!
I guess the thing what surprised me the most was the costs of the add on for the DLC's, and I know, you don't need it to play or even enjoy the game. It just feels like its a "Try this airport for £15 and if you like it, spend more to make it the finished version."
The other perspective I have is that because it's a niche market you are putting potential customers off because of the price, if it was a little cheaper I think people would be more encouraged to buy the DLC. You are correct though with the movie comparison too. I've certainly had a lot of enjoyment off the original 3 so far! Apologies if I came across in a bitter way, like I said, I'm new around here and the prices just surprised me! The devs of course need to fund the next version somehow, sorry I flex off the handle!