Well at least better than a many a mileage run in terms of points per dollar (you don't get to visit some place new or accrue points toward upgrading your tier status).

From October 1, 2000 through January 31, 2001, you can earn double
Executive Club miles - 1,000 miles total - every time you rent from Avis
worldwide. To qualify for double miles, you must rent on qualifying rates
linked to your Executive Club/Avis Worldwide Discount (AWD) number,
B335100, and provide your Executive Club number at the Avis counter at time
of rental. To find out more, go to http://britishairways.com/avisdouble.

I just priced the cheapest avis car(a geo metro out of STL) and under the qualifying rate including tax the price per mile is
about 1.7 cents. That is before any coupons are applied. The deal runs for several months so quite a few miles can be picked up.

If one did 100 rentals(and I am not suggesting that anyone will) for a cost of about $1,700 it would be enough miles to earn a BA F RT to Europe that normally prices in the $5-7K range. To me that seems like a good deal especially for someone who is working on accumulating miles for that special honeymoon trip or something like that.

I wonder if there is a way to further reduce cost basis and donate the use of the car rental to a charity for the day or something similar rather than just park it on the street until you need to return it next day.

Anyone have any ideas how to further reduce the price of the rental and make this an even better deal?