Clever use of free marketing: The band Atomic Tom performing on a subway with iPhones

The band Atomic Tom performing live on a NYC subway using iPhone instruments. It's a clever marketing ploy that has garnered them over 1 million youtube views. Clearly this was planned because they are all plugged into some type PA system. What did this cost them to produce and post? The cost of the iPhones.

I wonder what this will do for them. I will have to check back in 6 months.