Why is the cost of a typical nightguard for bruxism in the hundreds of dollars when it takes minutes for the patient in the chair?

Cost of treatment: The cost of treatment is based upon not only the time in the chair but the knowledge, training and experience of the dentist as well as the cost of fabrication and time spent behind the scenes, not to mention overhead costs typical with any business.

Professional Service: You're equating cost to time in the chair... A lot more goes into the fabrication of the prosthesis than your chair time. Experience, overhead, and responsibility for your care all play a part. A well fitting guard is priceless in protecting your teeth from parafunctional forces; it would cost a whole lot more to restore a dentition that fell apart.

Time does not equate: The time for taking an impression does not really tell you what goes on behind the scenes and the expertise that is involved in constructing a custom mouthpiece. Sure you can go online or some local retail store an get a mouthpiece, but this mouthpiece may not fit as well, and may actually make your bruxism worse by creating more intense muscle spasms. You get what you paid for.