For the most part the pricing will remain the same for the solo practitioner. Perhaps it might be fair to charge $400 for each additional user (when there are more than say 3 users) yet AC in my opinion is really geared more to a small office than a large group practice. However, if I were still in a 2 or 4 person group (like I used to be) I think the $500 per provider would not be unreasonable. That is only $42 a month, which is not a lot. And in that size group the program would work quite well.
