I know that Home Depot offers installation on these, as does Lowes. Ceiling mount hardware is pretty cheap and as long as you adequately template out ahead of time where everything has to go, it's not that hard. Make sure you're leaving extra room for the finial (the decorative piece on the end of the rod) on each angle, or if you're buying a bay window rod, ensure your measurements are good (or buy it from a place that will let you can return it).

Installation cost shouldn't be more than a couple hundred.