I think I see his point, but I think he's forgetting about the privilege of making good money at Google for a while and becoming an ex-Googler for all his life.
I can say that the people who say this DO NOT keep an excel on their desktop where every 1st of the month they go around their accounts, investments, etc. and enter the 'updated values' and they see their net-worth growing month-by-month. Money matters (when you are planning your vacations, when you get seriously ill, when you want to buy a new house/car/laptop), etc. Only naive people say that money don't matter. There are MANY things that matter, money is one of them.
The point is that it isn't money that makes you happy, it is the life you build. That can be different for different people, and money can help. The point is that money isn't the goal.
I've been poor for a long time. Trust me, daydreaming about money fixing all the problems is one of the biggest if not the biggest time killer/entertainment.
What I noticed climbing the ladder is that some people are happy and some people are sad independently of the income. And if much it seems that I met happier people in general when I was poor than now. I was happy in my poorest time and I'm still happy, which helps me see through it without the constraints of money.
Understood to mean (in the context of this blog) the difference in living standards and happiness are not affected by a 150k/year income or a 450k/year income. Or another way, "I (author) have encountered the diminishing return on happiness. dH/dm = 0".
Then you can bring those sheets together. What I did was combine my expenses across my debit card and credit card, then sort them into categories. Subscriptions, grocery (I shop at 2-4 stores regularly), hobbies, restaurants, etc.
I made a calculator in the sheet to convert my biweekly pay into monthly income. (there's slightly more than 2 pay periods per month, because a pay period is usually 28 days. I don't recall the exact number.) Once you have that, you can normalize all your expenses as well. For example, add up everything you spent on groceries in a 6 month period, divide it by 6. That's your mean monthly grocery bill.
It's a bit of work to get it all down but once you build the calculator it's not as much work to maintain it every month or six. I was able to figure out what it costs to maintain my lifestyle more or less, and then determine an amount I'm comfortable having automatically transferred to my savings account immediately after every paycheck comes through. (For me that also includes an amount that will go toward rent as I pay rent out of my savings account to ensure I never accidentally don't have money available.) Now I don't have to think about my savings often, I know it's going up at a certain rate. This also allowed me to take on some significant extra expenses to support my partner for a period of time without any fear.
Once you have enough money for basics and contingencies, yes, happiness is more important.
"Money doesn't buy you happiness, but lack of money does buy you misery!"
Anyone "rich" who forgets this is inhaling their success too deeply and is not acknowledging their good fortune.