The most reliable ball machines in the business is Sports Tutor, I own a Tennis Tutor Plus Player with Multi Function Remote Control, I paid under 2k for a demo model. Easy to use, very powerful and the player mode is the best feature giving me a random workout every time.
And the service department is the best when ever I contact them, for example the other day I called them because I smacked the front flap and broke it hitting overhead smashes. I called them and the said No Charge as in free! Plus they paid the shipping and they also told these flaps are covered for the life of the machine along with other parts on the machine as well. I LIKE THAT!