It depends on the area that you live in and the instructors that are available. Some instructors are just more expensive. In my area of Pensacola Florida $400 just got you knocked in the head... Open Water is $179 and includes tuition, books, video/audio discs, log book, dive tables, equipment rental, dives and card fees... This dive shop is one of the best if not the best in the area also. They are not there to make money, they are there to promote diving. Heck here in Djibouti Africa, a 3rd world country, the price is cheaper than $400.... Make sure you talk to the people who run the shop, do the certification and the customers who have been certified by them. Good luck and check around...
What shop is this and what is the OW course schedule (how many hours in the pool, classroom, and on dives)? Either their instructors are working for free or the shop is losing a lot of money on their OW classes.