only prices is in server.. and there is a flag in the database as well called monopoly in the cq_itemtype table.. value 28 seems to be shoppingmall flag.. but im not sure..
the xos u can buy from oltgroom has another value in that column
so basically.. if u add it to the shop.dat and change monopoly to 28 u should be able to buy it from shoppingmall.. (i want to add 6,8,12,19 star xos and specialexpballs,rebspheres and luckpotions)
there is no other table containing anything about shoppingmall or prices of items except itemtype table
there is also a column called something like maxbuytimes.. 12,19 star xo has 1 in that column so increasing it would let you buy more than one/day
dont be too sure that its serverbased only.. i think its a mix