I don't use a Robber or a Ninja in my parties, so in order to pay for "All Skills" for my characters (in this game, although not in MM4, this includes the Thievery skill), I use one of the unlisted codewords for the transport mirrors to get at some early money( ), but I have to use Mr. Wizard to get back again.I found that there was an XP penalty when I used Mr Wizard, so now using the procedure is the first thing I do, before I have any XP, so there can be no penalty.
Maybe your game is different?