"The F-150 carries a base price of $28,495, which is below average for a full-size pickup truck." This is just a quick search from Google. I think ppl might have different opinion of the word "luxury". But generally I would personally not categorize things that's widely sold like F-150 or iPhone as luxury.

I’d gauge luxury on necessity, not commonness.

It's a bit of both, and subjective, imo.

As an example, pretty much every item of food is "luxury" if based on necessity alone. From bread to the cheapest vegetable in your location - except for items that might be the only locally available/affordable way of getting certain essential nutrients, you don't need that specific food for a healthy life.

But... if that food can only be grown on the other side of the world, and therefore is in short supply and/or very expensive relative to local wealth: suddenly maybe that vegetable, type of meat, or whatever is considered a luxury without becoming more of a dietary necessity.

Would the cheapest, most common Casio watch available be a luxury because I don't need to have the time on my wrist?

As to the subjective/contextual side: I don't know anything about pickups, but I consider my car a luxury to me, and yes that's more to do with necessity than cost - it's not a fancy car, I could afford a much more expensive one, but I very much don't need it. I've never used it in relation to work, I get my groceries delivered, etc. (But while I'd call it a luxury for my life, if asked what kind of car I have I'd never call it a "luxury car".)

When you say iPhone, just consider you are speaking about a product which starts at $399.

Xfinity Mobile as an example:

$200 off the list price of the $399 iPhone SE. $8.33/month, with 0% APR for 24 months.

It has similar specs of a $1000 iPhone from a few years ago and is faster than any Android device you could buy for the same price.

Most carriers have the same deal.