I have a Dolphin/Maytronics Proteus DX4 and, for me, it checks the box towards having a trouble free pool. I have it set to run a 2 hour cycle every day and I only remove it to clean it or when we swim... or untangle the cord. lol
We have 20+ year old oak trees on each end of our pool so between the trees, squirrels and birds there is something in the pool every day either on the pool floor or floating that needs to be cleaned out. Having just had our pool resurfaced in an Aqua Blue Pebble Sheen finish, the last thing that I want is anything sitting on the pool floor long enough to leave a stain. Granted, organic stains would "bleach out" over time, it's still uncomfortable given the cost of the new finish.
One thing that I have found surprising is the amount of dirt/dust that is blown into the pool, especially when a storm passes through. Pool floor doesn't look dirty, but then running the robot and checking the filters is somewhat surprising. Not sure if the OP has issues with blowing dust/dust storms there in Las Vegas.
As for ownership costs, in the almost 4 years of robot ownership I have replaced the tracks and the front (larger) wheels due to wear. (knock on wood) As I mentioned, I run it seven days a week year round, so probably accelerated wear and tear in my case.
Ultimately, for me, it comes down to the time and effort that the robot saves me - sure I still have to brush the steps, bench and glass waterline tiles, but it takes care of the floor and walls and saves me from having to brush and manually vacuuming the floor. In my situation, I know that at a moments notice if we decide to use the pool, I know that there's no prep, from a surface cleaning standpoint, that I need to do before we jump in.
Value is relative to each person, so as the saying goes, your mileage may vary.
Hope that this helps in some way, or another.