What V said about the data samples. There prices can flux wildly. I never discard any. I used to use a lot in crafting, then donating to fleet or giving to alt chars or friends. Some can also be used for fleet projects.
It would be more proper to let the fleet leader(s) know why you are leaving. If they are mature, they will accept your reasons. It's been my experience that you will enjoy a fleet more if you choose the fleet vs you accepting a blind fleet invite.