Phone sales in general shoot up toward the end of the year. Promotions are taking place, the "holiday season" is starting... Every year it's the same drill. The 6S sales were nothing out of the ordinary. Now, if you'd told me that 6S sales were greater than 7 sales, you'd have a point. But the "better" device dramatically outsold the "inferior" device, which will always be the case, especially with Apple products.
In the UK the iPhone 7 sales were below expectation last year with iPhone 6S above expectation. This was my point and I know it's different in each country but we are Europes largest market. The BBC reported the chairman of Carphone Warehouse blamed consumers reaction to the loss of headphone jack but other reports suggest rising prices are to blame. People are keeping phones longer as spec jumps are stagnated and handsets are becoming more expensive. The fact that this time last year saw a spike in sales for the 6S proves the iPhone 7 did not get the same level of interest as previous models. In my country the 'better' device did not dramatically outsell the perceived 'inferior' 6S so I do have a point here.
We are about to see a £1k iPhone hitting stores in a couple of weeks and it'll be interesting if price plays a part in its reception. We don't get iPhone promotions here either. Their price is fixed and non negotiable with carriers.