And you could have earned even more than that in the time it took you to learn all the stuff that allows you to make $100 in that amount of time.
I could have made thousands of dollars digging ditches in the time it took me to learn everything that I needed to know in order to make $100/hr, but that wouldn't have made it worth while in the long run.
I also could have made thousands of dollars in the time it took me to read some philosophy books that never netted me any money directly, but that wouldn't have made it worth it either.
Sometimes it is just worth it to learn a new concept or think in a way you hadn't thought before.
I hear this a lot from shoddy engineers (my field, but equally true in other fields) who can't be bothered to learn anything new unless it's on the company's dime because their time is somehow worth too much to take the time to learn more.
This pervasive attitude that only what makes you the most money in the here-and-now is all that's worth doing is a real problem.