DMs, what would you charge for a Continual Flame from an NPC caster?

[Cyclops08]

I had this idea of a cleric with a continual flame cast on top of his helmet. when he wanted it gone he would just place a leather cap on his helmet.
Cap on, Cap off, the Capper.

Magic levels vary from world to world...whats the rate on yours?

[John Out West]

Well it costs 50gp in ruby dust in 5e, so it costs about 50gp and a good persuasion check.

In my universe we use silver as the prime currency, so its somewhere between 50 and 500 silver dollars, depending on where its sold, how common it is in the area, and how in-demand it is. On the sunny surface in a large city, I'd say 50 Silver Dollars. In the Underdark in a small town its about 500 Silver Dollars.

[Dragons_Ire]

In a major city with a temple, you could get that for 150 gp. Anywhere else? You'll have a tough time finding a cleric who can cast it.