I used to be a Windows user (95-XP). 18 months ago or so, I finally changed to a Mac, after wanting to for a while before (but couldn't afford the one I wanted).
As rojash says, comparing like for like makes them very competitively priced. You know that any Mac you buy can do video editing, and anything else more strenuous for a computer.
However, cheaper PCs are very definitely available, and will be more than enough for the vast majority of uses. The only issue here is that the RAM or something is skimped on, leading the user to post questions at places like here asking why they can't do video editing or something else they didn't plan or think about but now want to do. (And thus spend more money buying new parts).
Response to zinnie's answer:
1. True, however the vast majority of people don't want to upgrade, so it's a null issue for most. Computers are appliances, and less so these things for techies as they were 10 years ago.
2. Kind of true, but Apple have their own good stores and will pick up and deliver Macs for you (their phone support is great).
3. I agree entirely. But kids are smart and pick up differences very fast. Anyway, they're not that different.
4. Again, it'll take you a week or two of use and you'll forget your old Windows ways.
Games are a sore point. Good simpler games are available, as well as plenty for young kids. But the latest games your average 14 year old wants to play are Windows only. If that's too bad, then get a Windows machine.
Just remember that you're not just paying for some metal and microchips. You're paying for something that has a better operating system that's easier to use. It doesn't get viruses. You don't need to run a spyware remover every week. It'll cause you less stress.
(You know what I think you should buy :P)