Despite the fact that iPhone X is currently seeing strong pre-orders in Asia Pacific, many channel operators are still concerned about iPhone X's sales in the region since the model is the most expensive iPhone device ever launched and the retail prices of iPhone X in the region are about NT$6,000 (US$199) higher than that available in the US on average, according to sources from retail channels in Taiwan.

The amount of the pre-orders for iPhone X in China has exceeded one million units, and globally total pre-orders have surpassed 5.5 million units indicating that iPhone X is heading for brisk sales, said the sources.

However, the sources warned that phenomenal demand for iPhone X might fade away rapidly after the first wave of the buying spree triggered by replacement demand is over.

Meanwhile, the price gap for iPhone X sold in the US and Asia Pacific region might trigger resentment among consumers in Asia Pacific later, undermining the buying willingness for iPhone X, the sources commented.

The higher-than-expected pre-orders also pose a challenge to Apple, as sales of iPhone X devices would be affected if Apple fails to deliver these pre-orders in time, the sources said.

Due to supply constraints, some market watchers have indicated that Apple might not be able to fulfill all of the pre-orders until the first quarter of 2018.