Here's the thing, a monitor is going to be more expensive because it's a much better panel than the ones that are in lcd tvs. Even though it is going to have the same inputs of a lcd tv, the resolution is often 2560x1600 as compared to 1920x1080(if it's even 1080p). Since the resolution is so much higher for the monitors, the pixel pitch is often much much smaller (again a better panel). Lcd tvs will often have integrated tuners, since that is their intended purpose. Other than that, the only other real difference is that monitors are typically 60hz whereas you can find lcd tvs that will do 120hz (some even higher). The reason for the 120hz is "motion blur", usually an accommodation to the slower response time of lcd tvs. All in all, I think the answer to your question is a monitor is a monitor because it's a much better panel.
I wouldn't call PC monitors "better." Yes, they have a smaller dot pitch, because they are typically sold smaller in size. PC LCD monitors are usually 6 or 8-bit. Modern LCDs are minimum 8-bit, with the better ones today being 10-bit. Samsung 6+ and modern Sony Bravia are 12-bit dithered down to 10-bit output. PC Monitors offer better clarity due to being equal or higher resolution in a smaller size. HD televisions offer better color depth, range, and black/white levels. They're both great for their intended purposes. A PC Monitor is better for a PC desktop and fast paced gaming, but I'd always prefer an HDTV for movies.