When adding items to an NPC, you have 4 steps
1. Set the price of the item in the item.sdata
2. Set the price in the database Items table
3. Add items to the appropriate NPC in the npcquest.sdata files.
4. Be sure that the npcquest.sdata file in you client matches the one on the server side. These are quite literally the exact same files, just copy one to overwrite the other once changes have been made.
Bare in mind, I am still waking up. I may have missed something. If I haven't, then this should be all that is needed.
It sounds as if your npcquest.sdata files aren't matching. You only have the changes on the client side. Check the following folder:
D:\SHAIYA_SERVER\SERVER\PSM_Client\Bin\Data (assuming you have installed to the d: drive)
This is where you will find the server side file that needs to match that of your client.
Be aware that once you copy the client side file into that folder for the server side, if there are any flaws in the .sdata you just modified, your server will not start or may d/c you after character selection.