RPGs were more expensive than other games due to a combination of high development cost, high cartridge cost (RPGs took a lot of ROM storage), and relatively small market (action games were more popular).
Factored in with translation costs (or god forbid an included manual) and it's crazy these things even made it to the US in the first place. No wonder NES/SNES RPGs are in such short supply.
SNES games were $50-60 and that was thirty years ago!