Thx for your detailed post, fully agree on every aspect. But what really makes me hesitant to do the challenge is the addative pricing that you mentioned.

I'm European, based in Taiwan. Availability from TPE-IST is actually not bad, saw a lot of 65k J tickets. But only getting to IST doesn't do the trick for me as I need to go to central Europe more often than not.

So in the unlikely case that I would decide to commit to the challenge, I probably would do it as a combination of some trips in J and some in Y (I have a itinerary for around 7k USD) and just see it as a trip/holiday that would get me to a few places I haven't been before, while also earning me status & maybe paying for itself (not looking to use the miles for flights myself, would need to 'invite' some friends and family in the following three years).