I think the private J traveller is willing to spend a lot more than 3% of income.

It would come down to a) the disposable income and b) how that traveller value J-flights in relation to other ways of spending money.

The private J traveller is clearly putting a high value on traveling in J, probably finding it decent value even when someone else in the same income bracket would think it to be barely affordable. And people who travels a lot in their spare time probably aren't spending money on other "hobbies", ie having a greter disposable income.

I'd say the private J traveler isn't happy to drop the $4500 on the Z class trip, but not because he wanted to buy something else, but because he wanted it to be $2250 so he could do the trip twice!