Robin wrote:

precisely wrong: if you heed the warnings and register in advance or
within 3 days and pay the tolls there's no surcharge etc whatsoever.

Well, sort of. I realize all systems aren't the same. Here's the web page for
Colorado E470, the most recent system I've used.

https://www.e-470.com/Pages/HowE470W...ntal-Cars.aspx

Setting up an Express Toll account does requires the payment of a $35 deposit in
advance and you have to add the rental car plate number to the account before
driving on the toll road. A bit cumbersome and expensive for one off trips.