I agree that traveling more or less is a difference in degree not kind. But 'chongli suggested forgoing having kids so you can save money and travel. That's a difference in kind, and it's a prole sort of thing to do. At least assuming you'd otherwise have kids if you had more money.
Well, yeah. chongli's suggestion is a difference in kind, not degree, but I think his suggestion is a bit extreme. I don't think many people decide to not have kids just so that they can travel more. Plenty of people probably claim that, but I don't think many people who actually want kids would decide not to have kids just because of their retirement plans. There is probably a deeper fundamental lack of a desire for kids hidden in there somewhere.
Anyway, I think it is also worth considering how the price of having kids changes as you go up and down the income scale. Most parents will naturally be inclined to provide the best childhood for their kid that they can. For most people, this probably means making sure their kids have good nutrition, do well in school, etc. Parents with more money available to them might start considering additional expenses though, like private tutors, private schools, larger college funds, trust funds, etc. People with more money will probably spend more money on their kids, so that 50k extra (after taxes) income every year doesn't necessarily mean 50k more money for yourself. If your income increases, you'll probably spend more on your kids. (of course this won't make more income a wash, since certainly some of that extra income will be spent on yourself).
