Thievery has no cost because each act is gated. Once you finish an act, you can't go back to a previous one so you can simply not put any points in thievery until you are at the end of the act, then respec all your characters to max thievery and rob every merchant on every character. Then you can use hirelings to do the same all over again.
It doesn't matter who has loremaster in your party. You can open containers with your Lucky Charm guy and identify items with your Lucky Charm guy. Magic pockets will automatically transfer the ID glasses to your Loremaster guy who will identify it for you.
