I don't know any priests who own expensive cars. If anything the Trad priests I know have slightly better cars than the novus ordinarians. But seriously, what priest has a new Jag, S class Merc, E-class Merc or Lexus?
Perhaps Argentina is full of priests like this, but the UK is not.
Some Trad priests do a lot of miles. I am not sure it makes sense for them to be dealing with breakdowns and repairs instead of giving people the sacraments. Think of them like sales reps, who are doing a job that is far more important than the devaluation of their car. No company buys their sales reps cheap second hand cars, because that is being penny-wise pound foolish.
There is a shortage of priests. The last thing we need is them stuck at home because their car has broken down or queuing for a bus. Specifically, on the question of Trad priests, a significant number of them have been killed at the wheel in road accidents over the years. I would not begrudge a road warrior priest a $30,000 car as opposed to a $20,000 (cheap) car.
In addition, if you do any serious miles in a car, you will get tired and uncomfortable.
Take my word for it, if you have never done it, but 1000 miles per week in a decent car with less wind noise, road noise, vibration leaves one a lot less tired than 1000 miles in a cheap car.
If Francis wants to save money he should kick out the perverts causing the church to get sued every few weeks.