I feel the $$$ pain. We decided to go to SoCal in August almost last minute (3 weeks prior), and when booking the rental car, it cost us $350 for the week for a standard size car. For our upcoming trip in March 2011, I booked it earlier this week and got a standard SUV for $268 for a week. What a difference.
For your brother, since you're so close to the trip date, you can probably try to use a Costco code (if you belong) for Alamo or Budget. I find that to be the better rate for us. Or use one of those codes in Mousesavers.com. But you're right - you are going to pay more if your pick-up location is different than your drop-off.
Oh, one more thing, you'd better hop to it. When I was checking 1-2 weeks prior to leaving for our trip last August, my expensive $350 standard size car rental jumped to $400+!!!
Good luck!