Having Permanency cast would be daft: not only is the spell not on the list of spells that can usually be made permanent, it's an expensive way to get the effect you're after. The minimum of 500XP for a permanent spell would make it cost 2,500gp (5gp per xp), plus 450gp minimum for the fact that permanency is a 5th-level spell, plus 45gp minimum for the 9th-level caster to cast light. That's a whopping 2,945gp.
If you follow the guidelines for magic item creation, you could create a permanent Light such as you describe using the Create Wondrous Item feat. That would result in a base price of 1,500gp.
Of course, this is still way too much: there's already a 3rd-level spell that does something practically identical; continual flame. That has a 50gp material component and would cost another 150gp if an NPC cast it for you. So the most such an item would be worth, reasonably, is 200gp market price, regardless of how expensive an option you chose to make it happen.