My npc sell but it not cost

I have a npc on my server he sell stuff but it say it cost 100 but it not take any money from player

i use a darkrp mod with some changes

and i use this npc
http://www.facepunch.com/threads/955742-ShopMod-Lightweight-NPC-Shop-System

Go to this thread : http://www.facepunch.com/threads/955742-ShopMod-Lightweight-NPC-Shop-System
Step 2: Read the part about bugs
Step 3: ???
Step 4: Close your Darkrp server
Step 5: Profit