One way car rental?

I need to pick-up a mid-size car at Denver, CO Airport on 7/5/07 at noon, and drop it at Portland, OR Airport on 7/19/07 at 6:30 AM. I've been to Travelocity, Orbitz, Yahoo Travel, Priceline, and even my local travel agent. The best that anyone can offer is $875.00 with Budget Rent-A-Car. That's awfully high!

Does anyone out there have an alternative from these "main stream" rental options?

Many thanks for your answer.

One-way rentals are usually more expensive anyway. However, I've found that Enterprise is a little cheaper in general. Also, if there is ANY WAY that you can pick up the car at a non-airport location (like take a taxi to a nearby suburban location), that can make it cheaper as well. Check out their website for alternative locations and see if the prices are any better. Same thing with dropping it off.