Hi Stacy!
First, I apologize for taking such a long time to respond to your question. I wanted to give you the best answer possible, so I was following up on a few things with runDisney.
To be honest, there is not a reason, right now, for the prices to be any higher when booking through WDW-IRUN. Obviously, I don't know which Resort you were pricing, or where you were getting the other numbers (travel agent, website, etc.), BUT, I can tell you that if I were you, I would book the best deal possible.
Sometimes, runDisney will offer special gifts when booking with 407-WDW-IRUN, but right now, there are none for Princess Half Marathon weekend 2014. (as always, things are subject to change)
I like to watch the
Disney Special Offers page to see what kind of deals come up. Usually, if there is one that applies to my trip, I can apply it to an existing reservation. Since all of the Disney World Resorts will be host resorts, offering bus transportation to race events, for Princess Half weekend next year, you can book wherever your heart (and wallet) prefer!
I hope this helps! Please let me know if you have any other questions.