What do the starred upgrades mean?

Question

Some of the upgrades in the Payday: The Heist have a star next to them. What does this mean? Is there some kind of prerequisite for it different from upgrading normally?

Answer 1

Starred upgrades can be toggled on and off by clicking on the star.

The reason is that these upgrades change the appearance of the weapon in a way that some players might not prefer. For example, if you'd prefer to use the simpler iron sights instead of the upgraded reflex sight on your M4 / AMCAR, you still can, even after passing the point in the upgrade tree where the reflex sight is applied to the weapon.

Cosmetic changes to weapons do not affect the underlying stat - for example, if you toggle off the damage upgrade for the revolver, the graphic will show the old style bullets, but you will still deal increased damage as if you had hollowpoints loaded. If you toggle off a functional upgrade (such as a reflex sight), your accuracy will still be increased, but obviously, you will lose the ability to use the sight.

Answer 2

The starred upgrades change the look of the weapons, in addition to changing their attributes. For instance, a starred accuracy upgrade might add a scope, while a starred ammo capacity upgrade might add a physically extended magazine.

There are some photos in this article that show the guns and the parts that change with the addition of the starred upgrades.