I used to like pickpocketing back the gold after I got training, but found out that now I get a 0% chance of pickpocketing it back. Did Beth wise up to this exploit?
Curious as to why this is in the Dawnguard Forum, but to answer your question, after you pay more than a certain amount $2000? It is not possible to pick pocket it back. Try pick pocketing after each training session.
Paralyze them first in the moments the effect ends you can pickpocket anything off them even if it says 0%. I used that trick to give Hadvar the jagged crown, complete the quest then return and take the crown back.