Ceramic Coating is an extra layer of protection on top of your clear coat (and glass or plastics if you want). There is a lot of good material out there for what it does, but it more or less fills in any imperfections in the clear coat and creates a harder layer of protection. When I say fill in, it does not hide any imperfections like swirls or scratches. According to Avalon King, their product (and likely the same for cQuartz and others) is harder than the clear coat so it does not scratch quite as easily. It is also extremely hydrophobic. So it makes cleaning the car easier as well.
As for pricing, I paid $45 for my application. It is normally $70, but they had an intro pricing deal for first timers and I snagged it up. Applying the Ceramic Coating is really no different than applying a liquid wax. You rub an amount on one panel at a time, wait ~5 minutes, then buff it off with a microfiber towel.
Where most of the cost comes from when you are looking to pay someone to do the coating is the prep work. Because Ceramic Coating is adding a layer of protection, if your paint/clear coat is not perfect before you coating, it wont be perfect after. So depending on how much prep work your car needs determines how much a professional shop would pay.
Seeing how easy it is to do all of these steps though, I would never pay a shop to do this work. I have a cheap dual action orbital from Harbor Freight and some decent pads from
Chemical Guys and a couple different polishes and such. All it takes is time, and I kind of enjoy it and certainly love the outcome. If we can get some decent weather soon (and it doesnt snow too much this week) I can get my wife to use her real camera to take some pictures rather than my phone.