On Fog Machines

Whenever I watch a concert I always ask myself if that smoke thingy is really necessary. Apparently it is as it is one of the stage effects. Looks cool from afar with the lights and all. Have you wondered how much a cool fog machine cost? It's not really much. Well there are expensive ones but what I found online is kinda cheaper but works like the high end one. I haven't seen it for myself though, but that was what the review says and I believe it. These are legit people who did the reviews.