In 2015 A#1 installs a new A/C system in my sister...

In 2015 A#1 installs a new A/C system in my sister's condo for $6,000. I'm thinking not a bad deal, we had them out to our house 2 years later and paid $10,000 for the system they put in our house. Fast forward to a few weeks ago. My sister calls and tells us her A/C is out. We say, that should be under warranty call A#1 back out and have them take a look at it. They come out and find that her drain line is stopped up so they flush it and are gone after spending about a half hour on site. They charged her $59 for the service charge (understandable) and then $390 for flushing the drain line. That seemed a bit high. Are there parts involved for that kind of service. Doesn't seem like there would be, seems a bit pricey for less than an hour of work. I would think that the $59 covers the sunk costs of having to get a tech out to a job site. After that I would think charging for actual hours (or half hours) spent on the task would be reasonable. But maybe I'm not being reasonable. Or maybe the going rate for an HVAC technician is $780/hour.
But that isn't the end of our story. Yesterday my sister calls and tells me that her A/C isn't working again, and that since the tech came out the system has become less and less effective every day. So, we call and have A#1 air out once again. I talked to them myself this time and they warn me that if the issue is not related to the original call there will be another $59 service call fee. It was no surprise that they charged the $59 again. But the new diagnosis is a leak in the coils and the charge to fix for labor alone, because parts are under warranty is $6000. It would have been $2,000 had the labor still been under warranty. Ouch. Why do they even bother to warranty parts without labor. And I guess it's going to take them 7 and a half hours to do the work. I'm basing this on their $780 hourly rate, but I'll spare everyone the math.
This may not be an unusual story for this company. I don't know. But, I feel as if my sister has been taken advantage of. You be the judge.