In post 858, DragonEater70 wrote: Explore the desert.
Both merchants may have rotating stock, so no guarantees any of this will be available in future trips. Anything we can afford, we can buy today.
Additionally, it will cost either 500G or a Warp Totem: Desert to come here at all; if we're coming to shop in the future, I recommend exploring to find out what the merchants have that day.
We can test out the Skull Key on the door; doing this with exploration is an option (and will lock in entering the door).