I'm confused on why the value of an hour isn't just your hourly wage. If you value your time more, you'd be working less. If you value your time less, you'd be working more. Since you clearly spend exactly as much time working as you do, you value your free time that much.

Then again, that only works if you value the time you're trying to fall asleep or are asleep the same as you value work.

Back on topic: I've heard that taking melatonin makes your body produce less of it, though doing so the the point of having less total melatonin seems unlikely, and even if it's only a slight increase, it's only a few cents. Also, I didn't exactly hear it from a reliable source.