What exactly are you doing/buying and where? (And from who?) (And in what act of the game?)
There were a number of places that I had to change to make things free. Here is the list of what the PPF does:
Bartley the Trader (first trader in game)
- Buying equipment costs 0
- Breaking down magical items costs 0
- Upgrading items costs 0
NPC items cost 0
- Tested on NPC Dwarf who sells a key for 4000
- Tested on NPC woman who sells map for 400
Both of those NPC actions hit the same code to decrease your gold - so I thought it was a safe assumption that the same code would be called for any NPC who tries to sell you something.
I did not test the code on any other traders besides Bartley - so it's possible that a different trader calls different (unpatched) code.
(BTW - if you don't want to wait for a new patch, you can always start a new game, import your current character, go to Bartley, buy things for 0, sell for real amount, get a gajillion gold, then export character and re-import into your current save game.)