BUG: Locksmith and Sail Sale prices listed incorrectly

[Will]

During a Sail Sale, the prices listed for items at the Locksmith are incorrect: for example, the price for "1 key" is listed as 4, but the player actually ends up paying 3 when purchasing it.

Additional info:
- I did not have the Coupon Book item when purchasing from the Locksmith.
- I visited the Locksmith after activating the Sail Sale from the Observatory.
- It seems that the player is correctly paying half the original cost of the item (e.g. the "3 Keys" item normally costs 12, but the player pays 6 during a Sail Sale while the listed Sail price is 10); it's just the price listing that is incorrect.

Edit: Added additional info section.

[Steelflame]

Just a quick question. Did you happen to have Coupon book? Price will list as 4, but it refunds the coin back to you for the coupon effect.

[Will]

I did not have the coupon book, though that is a good point (I will update the original wording of this post to include this caveat). The other prices of the Locksmith are also incorrect (e.g. "3 keys" is listed as 10, but actually costs 6, similarly for "Special Key" and "Lockpick Set").