This has been an interesting thread and I have learned a few things.
The system I have came with my new F350. It was a TPMS/backup cam package. It is monitored on the Ford screen on the dash. They supplied the transmitter and valves and I had the RV dealer install the valves(internal readers) and rebalance the tires. He did not charge me for that. From this thread now I know why I don't have temperature readings.
As to cost, I had a Dodge van and a valve that rusted out causing air loss. Replacement one piece valve was over $90 ea. I installed a standard valve and then only monitored three tires. One by one all valves were eventually replaced that way.
My Ford truck had a valve develop a leak and theirs is a two piece valve. The valve piece was under $10 to replace.
As for batteries, it was my impression that with the internal units it is the spinning forces that give the valves the sending power, not batteries. Don't recall where I heard that. I don't get a reading until I start moving on either the truck or the trailer. I don't find that a problem as I keep a digital pressure gauge in my truck and can check them when I am stationary. It was checking them while moving that I always had problems with.
All in all I feel monitoring the trailer tires more important than the TV. I have had only one vehicle blowout in my life vs two trailer blowouts in 7 years towing 5th wheels.