After almost five years of manic one-upmanship following the initial release of the iPhone, one OEM has finally realized that the future of smartphones lays in the arms of everyday consumers. The Nokia Lumia 900, available today and priced at $450 off-contract (or between $0 and $99 on-contract), is the cheapest, high-performance smartphone that the world has ever seen, and a strong indicator that it’s high time for early adopters to step aside before they’re washed away by mom-and-pop consumers. In comparison, the 16GB iPhone 4S is $650, and the 16GB Galaxy Nexus is around $600.

The key word here is “high-performance,” rather than high-end. The Lumia 900 has a thoroughly middle-of-the-road spec — a 1.4GHz single-core Snapdragon S2 Scorpion (circa 2010!), 512MB of RAM, a 800×480 display, and 16GB of storage — but for Windows Phone 7, that’s ample. A penta-band MDM9200 Qualcomm radio provides LTE coverage in the US, and good worldwide 3G coverage. The only stand-out piece of hardware is the 8-megapixel, Carl Zeiss, capable-of-720p-video camera on the back — but to be honest, this is the one bit that Nokia couldn’t skimp on; WP7 might be able to give an old CPU a new lease of life, but what good is that if the phone has a crappy camera?

Of course there are trade-offs, too. By using older, cheaper hardware, the Lumia 900 is larger and heavier than the competition, and it also has a shorter battery life (7 hours of talk time vs. 8 on the iPhone 4S and 12 on the Galaxy Nexus). And, of course, the biggest hurdle of all is still Windows Phone 7.

I know this is a very tired argument, but you can’t escape the fact that WP7 has just a 4% share of the US smartphone market (and probably much less worldwide). The third-party developer ecosystem is simply incomparable to Android or iOS. While WP7 recently crossed the 70k mark, Android and iOS both have at least 500,000. As a result, WP7 misses official apps for services like HBO Go, Hulu, Sonos, Tweetdeck, and Dropbox.

There are major architectural absences, too. WP7 doesn’t support IPsec VPN at all, and doesn’t have built-in support for VoIP or video calling, or USB mass storage. Windows Phone 8, due out later this year, will fix most of these issues, though, and cross-compatibility with Windows 8 should resolve any app ecosystem issues.

In reality, though, many of these factors are the kind of thing that would put off upgrades or sidegrades — they’re not the kind of thing that a first-time smartphone buyer balks at. The Lumia 900 feels good in the hand, looks attractive, is very responsive, and has most of the features that a smartphone should have.

That’s the key point here: The Lumia 900 isn’t targeting iPhone or Galaxy users; it’s targeting the 41% of the US public who still own a feature phone. If you’re already firmly set on getting an iPhone, the Lumia won’t stop you — but for walk-in customers, the $200 price difference is really quite significant. For customers on the fence — if saving $200 isn’t enough — the Lumia has a bigger screen than the iPhone and a better camera than most Android phones — two factors that could easily sway people towards the Nokia device.

Other tech sites are calling the Lumia 900 a flagship phone, and thus comparing it to other flagships like the iPhone 4S — but that’s like comparing the latest Hyundai with a Ferrari. They’re both excellent cars/phones, but they appeal to wholly different categories of consumer. The Lumia 900 is $200 cheaper than the iPhone 4S!

In actual fact, there isn’t really anything that we can compare the Lumia 900 to. It’s a whole new class of phone — a commodity smartphone that’s priced and marketed for the masses. It has all the trappings of a smartphone, but a price closer to that of a dumbphone. In short, as long as Nokia and Microsoft can convince the masses that this is a smartphone, and yet not directly comparable to the iPhone or high-end Androids — and the “Beautifully Different” ad campaign does just that — the Lumia 900 should fly off the shelves.

On a related note, the $450 Lumia 900 all but confirms my suspicion that a $200 Windows 8 tablet will be available at launch. Much in the same way that the Lumia could redefine the smartphone, the Nokia Windows 8 tablet should redefine tablet computing.

Read the full Lumia 900 review at PC Mag, or read about the dumbphone revolution