Although exchange stores directly managed by the Imperial Court feature clearly marked prices for all goods, the prices they offer for goods sold to them are not high.
While the purchasing price of the same goods is also clearly marked, and the difference between selling and purchasing prices is not significant, it seems possible to buy cheaply here and resell for a profit elsewhere.
However, once goods are sold to the exchange store, buying them back cheaply becomes unlikely, as even though the shop posts clear prices, those cheap goods are often out of stock, and any items in limited quantity and at a good price have already been internally consumed by the shop's staff.
Even in the era before the Natural Disaster when resources were abundant, clerks dealing with scarce goods would still intercept them in advance and resell them to ticket scalpers for a profit.