What's really dishonest with AVIS is that they say on the rental agreement that "you have been given a choice of currencies and that you agreed to be invoiced in your home currency". Well if you book on their website, are a preferred, you go straight to your car and the first time you see anything is the contract in the car. They don't ask you when you're doing the booking, you aren't given any choice at any stage in the booking process and the only way to resolve it is to go back to the counter when you return the car. That deletes one of the main advantages of being preferred and requires you to add 15-20 minutes to your return time, whilst the agent figures out how to cancel the bill you never agreed to in the first place and bill you according to the rate you did agree to.
For heaven's sake if I am quoted a rate in USD, then bill me in USD. It shouldn't be that difficult!