Seems like they're trying to help you justify your warranty purchase. They aren't that expensive.
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I pay a few bucks more a month to not have t o work on my car or have to ever buy parts for it except wear items...and awesomely, not including shocks or struts---which this warranty covers---for 150K miles! It's worth it, regardless of the fact that even by your prices alone, I will get over $1,000 in mirror motors covered at this rate in 150K miles, lol.
That $741/per is what they showed on the bill when it was Mazda's OEM 3/36 that covered it. I have not gotten the bill for this one. When they did the work the first time, I requested the part and labor cost breakdown without warranty. It took them a couple of hours as I recall. Gotta take the door panel off and all sorts of BS to do the job.
You break just one tab on that inner door panel, and you're gonna be spending a lot more time and money. I actually helped build my first car in the driveway as a kid, and no, I doubt that motor is that much (they bill about half of that in parts though, and I've found I can buy Mazda parts online for about 80% of dealer pricing usually), but what IS expensive is the fact that many of these assemblies (door panels, etc.) all have a "trick" to them in how you press, pull, or flex the part. If you mess up in the pressure applied via force OR direction, you can easily snap one of the "hooks" or inserts, and then the door panel or whatever will not be as solid as it should, so inevitably you replace that, and mistakes add up FAST.
I remember one time trying to change the PCV valve on a friend's Jeep. It was pretty old. I broke a lot of rubber/plastic junk pulling it out of the grommet. It actually ended up costing me, to fix his jeep. Now, I know my 2019 isn't like that, but it's still a lesson.
Regardless, why don't one of you fine citizens go to your Mazda dealer's service counter and fact check me on them prices during your next oil change...