That analogy is desperately tortured. It just ... does not map at all to how I ever perceived reading or fun videos. I never even heard anyone talk about it is those terms.
The time spend by purely relaxing activities like reading or watching is on itself a reward. You do it instead of doing something less pleasant- staring bored at the wall.
And the idea that you could have spent all that time doing something super useful is wrong if it is about opportunity cost. I tried multiple times to cut off all "time wasters" like reading fiction or videos. It ended in low productivity and depression each time.
Imagine you could spend 16 hours enjoying reading without any time having passed in the real world. Then you would still have those 16 to enjoy something else as well. But instead you are actually 16 hours closer to your death. That's the cost. Not the time you experienced, but the time you no longer have.
If I would not be reading, that time would still pass. I would move closer to death by the exact same amount. Literally regardless of what I would do for 16 hours, my life would move exactly 16 hours closer to death.
The assumption is that if you wouldn't be reading, you could do something else that you would want to do. But if you are reading you can't. If you have more time than you know what to do with, then the argument doesn't hold.
I think we only say things about the cost of time for leisure activities when it's not worth it. Example, I heard many times people saying about a bad movie: wow, I wasted 2 hours watching that
The time spend by purely relaxing activities like reading or watching is on itself a reward. You do it instead of doing something less pleasant- staring bored at the wall.
And the idea that you could have spent all that time doing something super useful is wrong if it is about opportunity cost. I tried multiple times to cut off all "time wasters" like reading fiction or videos. It ended in low productivity and depression each time.