For a device that I'm using basically all day, everyday, I want the best on the market. That happens to be the iPhone. So it's worth my money. The other part is that there is no alternative to the iPhone for using iOS. While one can get a similar experience to a high-end Android from a much cheaper device, there is no such equivalent with iOS. I've tried cheap Androids and other alternatives in the past and they just don't compare.
Understandable however, if some can't afford it or don't use their phones enough to justify Apple's prices. That's why those alternatives exist.
The iPhone being the best on the market is debatable. Best for you, sure, but there's a ton of disagreement on what is the "best" smartphone. Some say iPhone, some say the Note 5, some say the Moto X etc. etc.
I've been on iPhone since 2009 and Android since 2010. Android has gotten a lot better over the years, as has the iPhone. At this point, most Android phones with the proper modifications work just as well as the iPhone.
I've had a Note 4 for a few months, almost gave up on it to go full Apple again with the iPhone 6S+. Instead I did a complete restore, installed a different launcher (interface) and the thing runs flawlessly. Just as well as my iPhone 6+ did. The camera is just as good, if not better in certain situations. The display is fantastic (easily better in terms of brightness/saturation to my eyes than my 6+ was). Having the ability to swap batteries, plus extra storage (through the microSD), and now a phone that just works...I'm not entirely sure I'll ever go full Apple again.
The days of Android being WAY behind iOS in terms of reliability are behind us. Again, with proper modifications, Android runs just as well as iOS. I also use an app to "mirror" and "send/receive" texts across multiple devices, just like iMessage.
In short, choose what's best for you. In my case, Android is doing me well for my smartphone usage, while I can't think of any reason to ever give up my MacBook as my primary laptop.