Average cost $45-900. As of 2014 Nitrous oxide known as laughing gas typically cost $45-$80. Oral sedation such as Valium, Xanax, (alprazolam) Ativan or Halcion cost about $150-$250. IV conscious sedation average cost is between $250-$450 depending on the length of the appointment. General anesthesia cost typically $500-$900 for the fist two hours. These fees may vary significantly by region, or even by area within the same city.
Varies. No "usual" fee to be universally applied. Why don't you contact an office in your town that offers sedation dentistry and ask them? You'll get a better answer from someone who can actually treat you.
Depends. The answer to this question all depends on the type of sedation and who is doing the sedation. There are multiple different types of sedation and levels of sedation in dentistry, and every dentist is going to have a different fee for these services. Sedation can range from antianxiety pills to the operating room. So its best to consult your dentist on what your expectations/goals are.