Consider that maybe happiness isn't about "personal happiness". If all that one needs to be happy is to not have stress, why question that and desire more? By questioning it, you're undermining the happiness. The goal shouldn't be to raise the happiness bar, it should be to lower it so that more people can experience happiness. Why should only those with significant means beyond the bare necessities have access to happiness?

If you're always questioning if you're happy enough, you'll never truly reach happiness.

So one obtains shelter, and healthcare, and an education, and all those things you listed. And they're still not happy? If cake is the baseline, is more icing going to make that much better?

And that was exactly my point as well. Once you are no longer anxious about those things, then, to use your own words, happiness becomes a question of what personally makes you happy.

I have observed that people who reach that state aren't looking for "more money" so much as they are looking for something that is more fulfilling for them personally. And the article observes that as well.