If you are considering a concept for an EV that people would drive on a daily basis, you should get in touch with the EAA. There is a Scottsdale chapter. A Basic Membership is only $35 a year ($25 for students).
There are typically a bunch of members who have done an EV conversion or are planning one. They are generally pretty enthusiastic about helping each other. It should not be very hard to find someone in your local group who can direct you to a more economical source for the batteries you need. You should be able to get larger batteries and in larger quantities than what you would want to buy from a hobby supplier. Someone should also be able to help you with other issues such as the Battery Management System (BMS) and chargers.
If you are lucky, you may be able to get in on a "group buy" where someone takes on the responsibility of importing several pallets of batteries then ships them to all the participants. One of the members here in Houston saved several thousand dollars this way.
www.electricauto.org