It depends on what the accessory is. If it's necessary for the transformation then I pretty much have to have it. If it's a targetmaster or secondary robot I'd rather have it than not. If it's a fairly generic part like a generic-looking gun then I really don't care.

I'm more likely to care about a missing sword or other weapon than a missing gun. Melee weapons are a bit unusual on Transformers (and swords are cooler than guns anyway), whereas I can usually find a gun lying around if the toy really needs it.

I could not care less about generic accessories such as those that come with Cyberverse Legion toys.