What is the approximate cost of removing a single graffity tag from a concrete or stone wall (no painting)?

I live in Montreal, Canada. The tag is approximately 3 feet diameter.

I know this depends on many factors, and on the company that removes it, but I want the best approximation you can give me. I have no idea how much that costs. I have never ever seen a price of a graffiti removal service. Just give me the best interval you can. Thanks for your answers!

Thanks for your answers so far. I know doing it myself would be easier and faster but I really need to know the approximate price from a removal service. I need someone who has an idea to give me an approximation. A link to a single graffiti removal service website with price estimates would be fine.

Yeap, it appears Canada has gangs. They are good boys though, they have nothing to do so they only make tags and walk around pretending to be bad boys. Montreal (my city) has an excessive amount of ugly graffiti tags in downtown. Too much for such a nice city :(

Just go to your local hardware store and pick up a can of paint remover in a spray form it'll cost $6.79 and make sure to get the water soluble kind.

I wouldn't even consider hiring someone else before i'd try to tackle the job myself. A wire brush (couple of bucks at a hardware store) and some "Elbow grease" should do it. Ok now - i'm just curious, You guys have gangs? In Canada? LOL!