Computer moniters have a diffrent aspect ratio 16:10 i belive also have a denser pixel ratio i have hooked my tv up and i can see a diffrence unless i switch it to game mode then its not as bad but moniter is way better.
16:10? You're very wrong.
I'll clear this up: A TV usually has more inputs like Coaxial cable (Cable TV); SCART (a very, VERY old cable standard unlike HDMI), YPbPr, composite video (you know, the yellow cable?).
Next to that it has functions like digital TV (atleast a lot of the latest ones which have a card reader) and channel browsing (some even have USB).
They generally have a higher response time too as they're mainly used for watching movies.
And I think that the pixels are usually larger than the ones on monitors too (kinda explains another factor, the smaller the pixels, the harder to make and thus more expensive but I could be way off).
A monitor just does what it has to do: HDMI/DVI/VGA or DisplayPort in, an LCD panel (atleast most of them are LCD) and a small OSD for calibrating and all.
But they're also a lot more precise, smaller pixels, lower response times, more PPI (pixels per inch).
But yeah, most TVs now might give you an monitor quality of 5 years ago (which was pretty good tbh, most people won't notice anything bad).