DisplaySearch says that manufacturing costs for small-sized AMOLEDs are currently about 10-20% higher than comparable LCDs. A 5" Full-HD AMOLED for example, costs 16% more than a comparable LCD one.
But improvement in production yields will lower the gap - and in fact DisplaySearch sees OLEDs becoming cheaper than LCDs within two years, when AMOLED production yields reach 90%. DisplaySearch also says sees OLED materials cost reductions, which will also reduce prices further.
It was always assumed that OLEDs could be made cheaper than LCDs as they do not require a backlight and they have fewer components (light diffusers, color filters, etc.). But the more difficult production methods kept AMOLED prices high.
Some estimate that next-generation production methods (for example ink-jet printing) will enable even cheaper AMOLED production.