The iPhone 6s Plus is priced as the market will bear for a phablet. Its pricing structure at entry level, which is where the iPhone 6s Plus and the iPad Pro bear a similarity, is roughly comparable to the Note 5, so it's within market range. If it weren't, it wouldn't sell. And sell, Apple products do.
Here is the thing, both these Apple products will receive Apple support and OS updates. You know, iOS updates. They won't need to go to....say....Android....to save their devices. So that's worth the money, as far as I'm concerned. The OS is viable, and I'm pretty certain that I'll be able to get the next one next year. In other words, it's not a dead end like other OSs. It's not like the Quasimodo and the Q10 I've got, sitting in a drawer and gathering dust; native app support is dead because the CEO told devs to just build for another platform, and the company is placing the majority of its attention into another OS from another company.
Apple support of iOS is worth the money. Customer service is worth the money. I can walk into an Apple store and resolve any issue I may have. Or call them directly without having to jump though hoops with third party companies outside the country that don't give a damn about the customer. And if I crack a screen or the screen lifts, it's taken care of. That's worth the money.
And the apps????? Oh lordy. Any app I want, I've got. I don't have to hack my phone to get them. And developers are developing for my phone, not some other company's phone that I'm pooching and putting into my device and hope to the high Heavens that it will work.
Let's talk about dependability. I was on a commuter train when my BlackBerry decided to die. It was a 9900 and yup, those bricked themselves with no warning. What saved me? My iPhone 4s. I've had not one single iPhone die on me. So I'll gladly pay 978 or thereabouts for an iPhone 6s Plus that I know will be supported, maintained, warrantied, run native apps from developers who build for the device, be there for me on the middle of a commute home, not have screens lifting (my ex's Quasimodo had his screen lift by the way, mine hasn't because it's in my kitchen drawer under the kneading roll because it's useless to me), and with an OS that I know will be there next year and not be EOL in favour of another platform in a Hail Mary attempt at keeping the company alive.
So......long story short......(too late)....I don't feel that the price on the iPhone 6s Plus nor the iPhone 6 nor the iPad Air nor the iPad Pro are overpriced. Their price is what the market will bear. Had they been on a dying platform, then a 500 price tag is too much. Which is, coincidentally, what the Quasimodo is going for. It's 500 bucks for a device that is, possibly, EOL, given the dearth of leaks and the noise coming from the CEO.