You should probably go to a different mechanic, that guy is nothing more than a parts monkey, replacing components on your car and hoping the issue will magically fix itself.
There are two reasons your brakes will stick, seized brake hardware, or seized caliper piston(s) because of bad brake fluid.
I'll give you the worst case scenario first.
Caliper piston is cocked sideways, the piston bore will be beyond repair- Need New caliper
Caliper piston is stuck, but the bore has heavy corrosion and scoring - Need new caliper
Caliper piston is stuck, but has light to no corrosion or scoring - A rebuild kit will fix this if available, if no rebuild kit is available, you need new calipers
Caliper pistons are fine but, caliper slide pins are seized - New caliper Hardware will fix the problem.
What's the cheapest way out of this?
If your caliper is bad, you can go to the junkyard, get a caliper, rotors, and pads for next to nothing. Make sure rotors do not have a lip on the outside edge, make sure brake pads are thick and even, also make sure the rotors are worn evenly,as in there is now tapper to the inside or outside edge
Check to see if caliper head shields and seals are intact too.
If all credentials are A-Ok, grab them. And give them to a shop that will allow you to have them installed.