tire pressure monitor systems

I have access to a fleet of vehicles to drive for the work I do. Most of these are equipped with the in wheel type pressure monitor systems. In the past two years no fewer than 6 of the vehicles have had a sensor failure in one wheel. This requires the dismount of the tire and replacement of the sensor. I seem to remember the invoice for one of the replacements was $280 parts and labor...but my memory isn't what it used to be. I know it was more than $100 because the fleet maintenance carrier had to be called to appprove the work.

For me I would go with the valve stem cap type external sensors just for the ease of replacement.