3D touch components for the OLED iPhone 8 are allegedly 150% more expensive than for the LCD ones
There is a serious difference between LCD and OLED displays, however, which apparently requires a different technique to be used for 3D Touch implementation. According to the Chinese media Economic Daily Times, with LCD panels the 3D Touch sensors are directly bonded on the panel, while with OLED, additional glass needs to be bonded on the front and back side of the display in order to strengthen it.
This allegedly made the manufacturers of said components raise the price for OLED-display iPhones by 150%. Currently, TPK Holdings and General Interface Solution charge Apple $7-9 per smartphone to produce the parts, but for the anniversary edition, the price has reportedly jumped to $18-22 per unit.
Whether or not this is true, and if there actually will be an iPhone with an OLED display has yet to be confirmed, so do take this information with a grain of salt.