They run 50% off during X hours rather regularly and probably do the same in other cities too, just fyi. Plus you can always check the fares between the two as sometimes Uber is less. I'm kind of practical so Uber black would be a waste of money and totally not necessary as who is going to see me arrive? No one and I don't care about that kind of stuff anyway.
It really turns out to be worth it, not having to deal with traffic, or finding a spot (because I detest valet... lol) and then hiking through the garage into the property with a large suitcase.
Yes, I live close and this is one of the reasons why, no commute so to speak. Which means there is savings on gas, driving time, wear & tear on the car, my car insurance rates are less too.
But it really boils down to how I want to spend my time. It's super valuable and I don't want to spend it sitting in traffic.

I realize though, that the majority of Vegas has a commute so that won't be the case for most everyone.
Plus, you get to support a small local business (the drivers) instead of some person in casino accounting who is in charge of tabulating the parking revenue. Win-win