I've been sending damage droids to kashyyyk in the second slot a bunch, after luckily unlocking Chiss HSP on bronze.
Now other than the usual VIP and credit rewards, sometimes I'm given the message that I've already opened this cargo and to please have these bux. It started out at 2 and it's up to 12 now, increment of 2 each time.
Has anybody else seen this yet? Maybe it's because I've unlocked a level already? I don't know if you can get other levels from different areas.