Regardless of whether price is based on battery life, it has been shown that price is based on who the customer is and the circumstances. Uber is modeling base

Regardless of whether price is based on battery life, it has been shown that price is based on who the customer is and the circumstances. Uber is modeling based on willingness to pay. For example, others have shown that on average, a ride back home will cost more than a ride from home to somewhere else. Uber's algorithm has learned that if you are away from home without your car, you may have few other options, and you may be willing to accept an inflated price. While this does great things for Uber's short term revenue, it will absolutely destroy it long-term. If the drive to the restaurant is only $10, but the ride back is $40, people will remember this and just drive themselves the next time.