Materials and workmanship. What’s the difference between a cheap car and an expensive one?
A cheap watch usually has a plastic band, is plain, frequently has just a single dial and only tells time. $8 watch
An expensive watch is a piece of jewelry.
It frequently has a metal or leather band, is much more decorative, has multiple dials and functions. $400 watch
And then you get into watches with gemstones or precious metals.
$1085 watch with diamonds
$4760 watch with diamonds, mother of pearl and 18karat gold