You could license Chinese IP for cheaper, maybe still with a per unit royalty but pretty low, or no royalty may be possible. Dunno what can be negociated or how you would conduct a negociation.
Then, forget about 28nm, you can't afford it. tunafish, don't you have to at least pay for one obscenely expensive mask? (if it works first time and doesn't need a revision)
I think you could get started for reasonably cheap using chinese MIPS on 65nm, for instance (you avoid paying an ARM license, and perf/watt is still pretty nice, there are Android 4.x tablets made with such SoC)