The problem is that due to the economy being the way it is, and less people traveling, the rental car companies have cut back on the number of cars in their fleet so few cars mean higher rates to meet their expenses.
I was at WDW June 13-20. The rates were high when I first booked, well over $200. They dropped in the last couple weeks before my trip, I ended up paying $150 incl tax for 8 days. That was National Emerald Aisle w/$35 off coupon. So don't give up, keep watching!
I found booking early sometimes help. When DH first started talking about going to WDW, I jumped on the web and started looking at car pricing. I made a ressie with Alamo for a midsize SUV for 11 days for $355/total for late October. I made that ressie on December 30th. Now the same ressie with the same codes is well over $700. I will continue to look, but I'm not holding my breath.
I booked a minivan for 11 days in January. I reserved it about 3 months ago with no coupon from National for $428 total. When I look now, I can't find the same van for under $1200! I am so glad I booked it when I did! I am afraid to even ask to apply a coupon to it, because I don't want to risk them screwing it up, and changing my rate!
Do you have a Costco card? I was able to find a car for my brother (fullsize) for a week in Sept. It was $196 incl. tax with Alamo.