Look guys, I'm only giving the OP the real numbers and the potential problems an solutions. I have done HVAC for 18 years. I have an engineering degree and I design commercial and residential HVAC systems. I run my own business which is very successful with many happy customers. You can run your system however you want. If you doubt my theory on letting the temperature rise then you are forgetting about thermal mass of objects as well as the humidity control. You don't just cool the air in your house, you also have to transfer the BTU's out of the items inside the home. Think of it like driving your car in stop and start traffic or setting the cruise control on the highway at 55. Which burns more gas? Try running a 5-8 degree set back. More than that and it is most likely not saving electricity. We like to see a 15-20 degree delta on our indoor coil. If you can overcome a large delta quickly on a 95+ degree day then your equipment is most like oversized for the application.
The EPA regulates the refrigerants and the supply house sells it to licensed contractors like myself. I didn't make the rules, I don't set the prices. I also don't gouge $100/lb for R22. The companies that are servicing your equipment have large overheads like vans, employees, shops, worker's comp, insurance, blah blah blah... They can't give it to you at cost.
I suspect that the system either has a leak or is potentially overcharged. To figure this out you need gauges, temperature probes, a sling psychrometer, a pressure enthalpy chart, and some good training. I also hope that the previous tech pulled a full vacuum down below 400 microns after he installed a new TXV. If not there may be moisture and contaminants in the system that causes damage. In order to properly charge a TXV heat pump it must be done in the cooling mode and sub cooling must be properly calculated. A proper charge is CRITICAL for getting the advertised efficiencies out of your equipment. HVAC is a highly skilled trade. There are basics that I described earlier, but it quickly gets complicated.
I always appreciate good help and insight from the members of this forum. I finally found a topic I can weigh in on, and people shoot try to shoot the shit out of my reply. Best wishes to the OP and feel free to ask any questions.