Robbery Payouts

I'm still working towards Master Thief 5, but I just did Rob the Chambers of the Duchess: Gleams in the darkness twice, and both times I got less than the 1000 Jade and 1000 Moon Pearls listed (latest is 675 of each, and 16 rats-on-a-string). Previously, Rob the Glim Shipment: Rob the glim ship paid out a lot less than the ~1300 Shards of glim (I think maybe 1000).

I'm not certain if the robberies pay out less while you're still in MYN, if the rewards are actually random and not fixed, or if the rewards are fixed and have actually changed in game.