Cups on inside of rear, and the cup noice on the road is really an irritant! I told my wife I just want to get 5k more miles on this set before getting new ones.
I found out why my 2008 MDX wears out (cups) tires after 35 to 40k miles. Even though I get alignments 4-5 times a year and tire re-balance and rotation at least twice a year. It is because the camber in the rear end is not adjustable.
You have not defined cupping properly, and cupping is not caused by improper aligmment.
Cupping (sometimes called scalloping) is a condition in which the tire wears unevenly around the circumference of the tire, as shown in these photos (you can find more info by clicking on them - it's written for trucks but the information applies equally to cars):
Cupping is NOT caused by alignment. It is caused by a problem with your car that allows the wheel to bounce around, rather than rolling smoothly, as you drive down the road. Problems that can cause cupping include wheels/tires out of balance, bad shocks, bad wheel bearings, or other suspension problems.
Improper alignment can cause tires to wear faster, and can cause them to wear unevenly across the width
of the tread, but that does not result in the cupping/scalloped wear pattern shown in the photos above.
It sounds like your car has a suspension problem, not an alignment problem. (And no car should need an alignment 4-5 times a year, unless your "roads" are unpaved and full of ruts and potholes.)
This is the problem with taking a car to a tire shop. They can do alignments just fine, but don't necessarily understand the potential problems with that particular car's suspension the way a dealer (or a really good independent mechanic) often does. Take it to a good dealer or independent, not a tire shop, and get the problem correctly identified and fixed.