Very funny ....
First: Both skills are not too expensive to train. There are no powerscrolls for both at all. It is more expensive to build the skills around cartho + lp.
Cartho: Sell your drawn maps back to the npc.
Lockpicking: If you include dungeon chests into your trainings, you could even make money with it. (Not to mention that you get sometimes a decent item for further imbuing and lots of magical items for unravelling.
Since the saphir-method is already mentioned for cartho ... you can use it for lockpicking, too. That way it would be possible to train up to GM with a chest.
Not to mention that you will be able to train lp and cartho on lvl 1-4 t-maps depending on your actual skill. You dont need to start with lvl 6 maps. The lower ones are good for training your timing and what to do when the chest popps out.