Well, I never felt Avis is an honest company so this is no surprise...
In the old days, the free weekend coupons did not require the % taxes and fees since the base was 0. Now, with the points and I guess with this coupon, they charge all the % taxes based on some arbitrary amount.
I have always wondered if Avis is really remitting the % taxes charged to us to the airport/city/county/state authorities.