Yes, these are one-time use missions that will grant you quite alot of items.
Lets say its a slicing mission, you will get the "prosperous" amount of items and both augments and a lockbox(es). Or if its a bioanalysm mission you´ll get both samples, compounds and some of those white-quality crafting items.
Watch out though, ppl are usually greedy and will demand alot of credits for them and often it will not be worth it, depends on what crew mission ofc. Some are usually more expensive than others.