It can be significantly less to reface depending on how many cabinets you have. In our old 50's built home, we had the old wood cabinets with hinges on the outside, etc. We had them refaced for $3800. They used the existing cabinet boxes and replaced all the doors. It really updated the kitchen and helped us sell the home a year later.

Generally less.

Most kitchen manufacturers would have stock cabinet doors.

Generally less but there are many caveats. As with many types of contractors, Refacing contractors will vary considerably in price. The larger national companies and those that advertise like crazy will generally be more expensive. A local company, or local owner of a national franchise (such as us), will generally cost less. Then, too, the material matters. Refacing with thermofoil will cost considerably less than refacing with factory-painted wood doors. It never hurts to investigate. Of course, check for references, visit previous jobs, and check online reviews such as in Angie's List and Houzz.

The reason for usually refacing is to avoid the mess of ripping out old cabinets so a pretty good saving usually.