Apple is not a sapphire manufacturer, but GT is, and this afforded GT the opportunity to go into this business with minimal capital risk. GT has expertise that Apple does not.
It sounds like GT thought the new process was ready for production and all they needed was the furnaces and plant, and then they failed to bring the plant on line and produce what was needed.... and is now blaming Apple for it.
Since Apple provided the money to build the plant, an exclusivity agreement doesn't seem "onerous" in the least. The "below market" prices allegation also seems appropriate-- given that GT purported to have a new technology that changed the economics making sapphire viable for new uses. The main challenge with sapphire is that it is expensive, and hard to make large pieces-- such as you would need for the front display of an iPhone.
The idea that Apple wielded "all the leverage" is silly. GT could simply walk way. There is no leverage in the case when the other party is not beholden or forced to do business with you. If GT had such a killer new process as to make phone faces at reasonable prices, then they could have gone to Motorola, Samsung or other potential customers. How does Apple have all the leverage when there's no requirement for GT to sign the deal?
It really sounds like this company bit off more than it could chew, couldn't meet the obligations it agreed to, and is now having sour grapes.