Your entire argument is specious.
There is nothing inherently different between one who purchases a device using IUP, and one who purchases a device via any other method. We all pay the same amount. Apple nets the same profit. Apple realizes payment from those customers who pay full price up front marginally quicker than those who do the IUP or carrier installment plans. This is true because Apple releases the device to the customers on the stated approval from the lending financial institution and have to wait for actual payment - but it's most likely a nit.
So tell me again what you paid for this privilege, real or imagined. And please tell me how I, paying full price for a phone am not negatively affected by having to wait for a new device, while you, using IUP, would be.
To arbitrarily create a pool of devices that would be made available to one class of customers over another would be discriminatory and unfairly penalizes non-IUP customers.
Again, does Best Buy, Target or Nordstroms have separate stock for their customers, based upon how they choose to pay?