Magic is common, but not cheap. Everyone knows a wizard can throw a fireball, but the vast majority of the population has never seen it happen. Magic is special, but you’re not going to awe the pants of anybody by casting Open/Close.
That said, magic items and spellcasting services cost their full listed price. It’s not cheap! High-level stuff is especially expensive, because high-level characters are rare. Most adventurers retire or die before they become uber-powerful.