LCD monitor vs TV?

[-Sandro-]

Please explain me this.

Why the heck a 37" LCD TV FULL HD with 3 HDMI 1 DVI 1 VGA, tuner and more costs $500 and a 30" PC monitor FULL HD with 1 HDMI e 1 DVI costs $1050?

I always knew TV cost a lot less but I can't understand why. Plus why are FULL HD monitors limited at 60hz? Tv could have several refresh rates, but I've read in a LG TV manual that if you hook up a PC via HDMI you can only get 60hz, but if you use TV tuner or HDMI device (such as player and decoders) you can have multiple refresh (50/60/72). Now how does the TV know you're using a PC source if it's HDMI in both cases?
There must be something different

The only resealable thing I could think of is that they don't want you to use TV and PC like a unique device, for example If I want to buy a cheap 37" FULL HD (that I can't definitely afford in the "monitor version") and use it as display with the PC (like a media center) I can't enjoy it. If a have a Blu-Ray device I can't show it at 72hz because the TV will use its PC mode and only show 60hz.
Thank you.