If your kid gets into byu, you can lower costs by NOT living in the dorms. It can also save money on meal plans (required at Helaman halls). I know kids who cover 99% of their school by working while attending BYU... it can be done. Even a part-time job will cover a good portion.
The problem is... It's not easy to get accepted into the school. If you don't have an acceptance letter in hand, you may want to find a few other backup options.