A pistol red dot is the upgrade most people buy twice, once on price and again after the first one fogs, dies, or will not fit the cut in the slide. Here is how the categories actually divide, and which optic belongs on which gun.
An LPVO is the most versatile optic you can bolt to a carbine and the easiest one to overpay for, because a 1-6x that costs a few hundred dollars and one that costs several thousand photograph identically. Here is what the category actually costs and what the money buys.