...because it never really needed to be bought:
http://dom.retrobox.eu/?/20130305/log.50635cc651c3843e7939ece8.1362516576804.txtKey cards: Thief, Band of Misfits, Procession, Border Village, Junk Dealer, Apprentice. Procession plus good $5s plus BV is quite amazing; Use Procession on a $5, gain a BV, gain the $5 back. Add in BoM to mimic Procession, and things get a bit crazy.
But after 9 or so turns I realized I had almost nothing in my deck except actions, and Junk Dealer to get a few coins at the expense of really expensive actions. My opponent, meanwhile, has gone not for pure Big Money, but for BM plus BV/Apprentice, which is close enough. Using BoM as both Procession and Thief makes short work of his cash, culminating in stealing a Platinum and a Gold before he could play them.
Also an excellent example where Thief is probably superior to NB.