Don't know if anything else is planned in Moab for events that would drive up motel prices, but the Apache isn't pricey and still pretty close to downtown. Usually doesn't fill up unless there's something big happening in town.
This is the only event I see listed for that weekend:
Thu-Sat 11-13 Canyonlands National Park 50th Anniversary Celebration - The Canyonlands 50th Anniversary will be a yearlong event that will culminate in mid-September, 2014. There will a variety of events through out the year with a main event the weekend of September 11th, 12th, & 13th. During this time there will be an historic film festival, a dutch oven community dinner, historic displays at the Museum of Moab, an art show at the MARC with a rededication ceremony at the Needles District of Canyonlands National Park. For more info visit bateswilson.org or call 435-259-0108.