You can buy an HDTV, a nice big one, for six hundred bucks. Or you can pay six thousand. It's presumably somehow better. You're probably wondering, "What the hell makes it better?" Here's the breakdown:
To be clear, we're only looking sets that are at least 46 inches—go big or go home. And though there are some nice 720p plasmas out there for amazing prices, the majority of TVs we're concerned with are 1080p—it's the standard now, even in cheap HDTVs, and probably the only resolution you'll see next year.
We focus on LCDs quite a bit here, not because we prefer them, but because there are key enhancements that can be put in LCD technology to make them look better. With plasma, the problems—energy consumption, weight, thickness—are more of an evolutionary, year-to-year thing. A cheaper plasma often is one that's just using older technology.
Also, we're using Amazon as our pricing base line, since it's on average a good standard for low but legitimate street prices, and we use Samsung examples a lot because they have a ton of different models on the market, so it was easier to isolate individual features, and to gauge subtle differences in pricing.
The first, and most obvious thing that'll cost you is more screen real estate. There's not an absolute inches to dollars ratio, but generally speaking, the first step up is the cheapest, and somewhere in the middle, there's a sweet spot, after which you basically lose money by upgrading. The funny thing is, each maker seems to have a different idea of where the sweet spot is, which you could play to your advantage:
Take for instance, Panasonic's plasma G10 series. It's $200 to go from the 42-inch model to 50, and then $400 to go up to 54. So the sweet spot is at 50 inches. Similar thing happening with Vizio's XVT line: Going from 42 to 47 inches is just $250, though going up to 55 from 47 costs about a a grand. Hence 47 inches makes the most dollar-per-inch sense if you like that TV.
With Sony and Samsung, though, it pays to keep going up. In Sony's top-of-the-line Bravia XBR9 series, the hop from 40 to 46 is $360, but going from 46 to 52 is just $250. Samsung's LED-backlit TV costs $350 to go from 40 to 46, and just $500 to go from there to 55 inches. (There's a limit, of course, Samsung's 65-inch LN65B650 doesn't have many of the frills discussed below, but still lists for $6000.)
The real lesson here: Don't think of size as a foregone conclusion. When you've narrowed down your options using all the criteria, go back and check the sizes and relative prices. There may be a surprise, hopefully good but possibly bad.
Everything after size you can roughly sweep everything you'd pay more for into the category of performance. The grand trick of buying TVs though, according to our friend Gary Merson of HD Guru, is that "the TV industry is setup like the car industry." Just like buying a Corvette to battle your mid-life crisis because it vrooms real good, when you pay extra money for extra horsepower, you're also going to get leather bucket seats and the in-dash GPS. It's hard to buy a stripped-down car that just delivers better performance, and the same goes when you're trying to scrimp on a TV without compromising picture. In the case of TVs, a higher performer might come with a million HDMI jacks or integrated Wi-Fi and video on demand, and you never know exactly what you're paying for.
Fortunately, we can break performance into a two major categories so it's slightly easier to interpret those price differentials: Backlight (for LCDs) and panel quality.
The single most expensive upgrade for LCD TVs right now is LED backlighting. As we explain here, there are a bunch of advantages to LED over conventional CCFL backlighting for LCD TVs. Which particular advantages you pick up depends on the kind of LED backlighting in the set. While both offer instant on and power savings, edge-lit models mainly deliver serious thinness, while backlit sets can offer local dimming, which delivers noticeably better black levels and contrast.