I think there's an implied "marginal" before both time and money in that statement. You have a steady income of time, you can choose to spend some of that on m

I think there's an implied "marginal" before both time and money in that statement. You have a steady income of time, you can choose to spend some of that on money, but past a certain point of wealth, the money ceases to be the most valuable use of your incoming time.