Since trunk r12264 you can alternatively use "cashshop" in place of "shop"
to use the Cash Shop interface, allowing you to buy items with special points
(Currently stored as account vars in global_reg #CASHPOINTS and #KAFRAPOINTS.)
This type of shop will not allow you to sell items at it, you may only
purchase items here. The layout used to define sale items still count, and
"<price>" refers to how many points will be spent purchasing the them.
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NakedWolf's post in Help Cash Shop NPC was marked as the answer