On Apple's (NASDAQ:AAPL) most recent earnings call, CEO Tim Cook said that "worldwide demand for both iPhone 7 and 7 Plus has significantly outpaced supply, particularly on the iPhone 7 Plus."

Apple's jet black iPhone 7 Plus is in high demand. Image source: Apple. 

Later in the call, when asked by an analyst whether the company expected to reach supply/demand balance by the end of the quarter with respect to both iPhone 7 and 7 Plus, Cook said:

It's hard to say. I believe that on iPhone 7 we will. On iPhone 7 Plus, I'm not sure. I wouldn't say yes at this point, because the underlying demand looks extremely strong on both products, but particularly on the iPhone 7 Plus versus our forecast going into the product launch.

For Apple, the fact that the iPhone 7 Plus is selling better than expected, compared with its expectations relative to the iPhone 7, is both a blessing and a curse. Here's why.

It's good to see strong demand for the Plus

The good news for Apple is that if the mix of iPhone 7 Plus it sells relative to iPhone 7 remains significantly higher throughout the current product cycle, then Apple could be looking at a not-so-trivial boost in average selling prices.

In the past, Apple's Plus models would sell for a $100 premium relative to their regular-sized counterparts -- already a hefty premium. This year, each iPhone 7 Plus model sells for a full $120 more than the corresponding iPhone 7 model, so the potential average selling price upside this year from a mix shift toward the Plus is much greater this time around than it was in prior cycles.

Indeed, had the mix of demand between the iPhone 7 and iPhone 7 Plus simply remained constant relative to prior generation models -- which is probably what Apple had planned for, as past performance is arguably the best indicator of future performance -- the $20 increase alone would have helped Apple's iPhone average selling prices.

But the combination of the higher average selling price and richer mix of unit shipments could prove quite a boon for the iDevice maker's iPhone revenue.

In a nutshell, the richer-than-expected mix of Plus sales, combined with the price increase on this year's Plus models relative to those from the last two product cycles, is obviously good news for Apple.

It'd be bad if Apple can't reach supply/demand balance during the quarter

Robust demand for higher-priced devices is good news, but if the company can't satisfy it in a timely fashion, that could potentially be bad news. Ideally, any demand for the iPhone 7 Plus that ultimately can't be met during the current quarter would just be pushed out to the following quarter. I suspect that this will be the case for most of the demand that's unmet during the quarter, but not for all of it.

Indeed, many of Apple's competitors release new flagship devices in the February-March time frame, so if a customer is stuck waiting too long to get his or her hands on the iPhone 7 Plus, he or she may simply decide to wait and see what the other smartphone vendors bring to the table -- lowering the odds that this customer will ultimately choose an iPhone 7 Plus.

In a nutshell, for Apple to maximize its iPhone revenue in 2017, it has to crank out more iPhone 7 Plus devices as quickly as possible.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.