It’s not only true if you don’t your free time. It’s only true if you’re a freelancer that is turning down hours at a higher rate than what you’re saving.

Many people working on products, both on their own and within a company, aren’t turning down other profitable work to optimize existing solutions.

If I watch a two hour movie instead of spending two hours saving $100/month, it doesn’t matter how much I value my time, no one is paying me $100/hour to watch a movie.