If I have a rental car, I stay off-site. I refuse to pay $130+ for a value room in addition to a parking fee! I have an AP, so don't pay to park at resorts. I can get an acceptable room for $70 a night, no parking fee and a $10 a night resort fee. The only thing I lose is having to wait for the Disney buses to finally arrive at my resort! My last trip to Orlando, I spent more time waiting for Disney buses than I spent driving from my off-site resort and parking the car! It was ridiculous. For people to say that this parking fee is the industry standard, perhaps then Disney should charge industry standards for their resorts!! I can pay $40 a night, off-site, for a room that is similar to the value resort rooms. Sure, I don't get MM amenities, but I can live with that for the money I'm saving.
And congestion on the roads? I didn't experience any massive congestion a week ago. It's a blatant money grab by Disney, designed to keep guests from renting cars. They get to keep the guest onsite as well as make a few addtl bucks a day per guest. A win-win for Disney.