After buying the 500 Rupee item, the Forbidden Woods Big Key was unbuyable and Totally Not Beedle kept saying this. Exiting the ship and reentering fixed it.
It seems that once you buy any item, he won't let you buy another one until you leave. Might only occur after you've already bought one item and then return (hence why Bombs are there)?
Definitely a minor issue, but it'd be nice to just remove whatever part of the code checks to see if you've already bought something and changes his dialogue to this.
