Just to add my two pennoth, as someone who isn't a flight sim fanatic (at least not on the scale as a lot of guys on here) but still bought it despite being skint. £50 (which when you add postage, VAT and so on is pretty much what I paid) is a lot for a game compared to the £34 you'd normally pay over here and frankly I generally won't pay for a game.
As I say, I'm not rolling in money, however I am a fan of 'nice' things, I like to have things that are good quality. Take shoes, I recently had a pair made for me for about twice the price of a pair off the shelf. They were however made to fit me, are excellent quality and will last near enough forever with proper care. They were crafted by experts to my specification rather than being slammed together in some sweatshop or pounded together by a machine.
My point is this; with OFF you are getting something that has been specially made, crafted to suit the needs of a community by very dedicated people who wanted to produce the best end product they could. You are not getting a crammed together 'off the shelf' job made by a massive company with no interest in player enjoyment but only in making money, you are getting almost a 'bespoke' game, something of quality, something that will last and you will enjoy for a long time.
At least that's what I'm telling the gf when she asks why I can't afford to take her out to dinner next week...
All that said, maybe you shouldn't be surprised that people who aren't particularly into flight sims are scheptical. They aren't particularly into the genre and so are unlikely to be as interested in the quality of the end product. It's a bit like someone complaining about your a bespoke suit just because it doesn't fit them.