A few years ago, during the middle of the D40/D40x/D60 progression, Nikon executives made a statement that essentially said "camera makers need to be ready to make and sell US$399 DSLRs." The implication was that those days were not far away. So where are those inexpensive cameras? Today we pretty much have the same US$599 price for low-end DSLR kits as we've had for years.
First, consider this: towards the end of film SLRs we had many models under the US$399 mark. True, film SLRs didn't have as much complex electronics in them, but they also had absurdly complex hand assembly issues and some fairly complex mechanical components, as well. It's difficult to reduce costs with difficult hand assembly. Yet somehow that's what we got. Indeed, the cost of assembly was one of the reasons why the consumer film SLRs started getting built in Thailand by Nikon: lower hourly wages and benefits.
Personally, I'm amazed at the intricate designs we're still dealing with in today's DSLRs. There's still an enormous amount of hand assembly involved, and your Nikon DSLR may have a couple of thousand parts or more in it. Is that necessary? No, it isn't. If you disassemble a NEX-3C and compare it to a D3100 you'll see that there's a big reduction in both parts and intricacy of assembly.
So why haven't we seen the camera makers push that and prices at the DSLR level?
Simple answer: they didn't have to.
At the time Nikon executives made their statement, Olympus was trying to push 4/3 DSLRs downward in price to try to build some meaningful market share. Seeing a US$499 kit from Olympus was a regular thing, even if it was not the latest and greatest camera they had launched. Since the most expensive part of a DSLR is the sensor, and since that cost increases logarithmically with size, the smaller Olympus sensor should have given them a pricing advantage, all else equal. Thus, one way to take the Nikon executive's statements was "we're going to match or beat you on price, Olympus, even with our sensor cost disadvantage."
But Olympus made no in-roads to beating the Canon/Nikon duopoly with their 4/3 DSLRs and about three years ago put their eggs instead into the m4/3 basket. Every now and again we see older m4/3 cameras on clearance hitting the US$399 kit price, but interestingly, even at that price those cameras don't climb to the top of the interchangeable camera sales list. What sits up there? The low-end Nikon and Canon models most of the time. Even in mirrorless-happy Japan that's the case.
In short, no one broke through the duopoly and caused the price drops Nikon (and likely Canon, as well) had anticipated. Even the Great Recession didn't break the price point. So is that a good thing or bad? It has attributes of both. On the good side, it means that Nikon retained product margins and probably even improved them at the low end. Things like CDs, manuals, straps, cables, etc., didn't disappear out of the box in an attempt to cut costs (okay, part of the manual disappeared to PDF form on the Web). Both Nikon and Canon seem to iterate the low-end cameras on yearly basis now, and we've seen them blossom from completely bare-bones, stripped down models to something somewhat more substantitve. The old iterate-slightly-upscale-but-keep-the-same-price-point methodology seems to be intact for the entire consumer DSLR lines. Nikon and Canon know how to do that quite well--it's one of the things that created the duopoly in the first place. The bad side is that we get small steps and no real rethink on the DSLR idea itself. A D3100 is recognizably a D40 with some new guts and features. The latest low-end Rebel is recognizably a Rebel with some new guts and features.
Two sources of DSLR buyers exist: new and upgrading. The new user is slowly declining, just as happened in film SLRs. Will every household have a DSLR? No. DSLRs aren't like TVs, radios, cell phones, or cars: they don't tend to sell in multiples per household. Thus, once the threshold of adaptation is neared, sales slow and mostly become due to our second DSLR user, the upgrader. Here, DSLRs have done better than film SLRs. With film SLRs there really was only one big advance that demanded updating: autofocus. The N8008s to N90s to F100 progression, for instance, was fairly subtle and centered on smaller advances. But the D100 to D200 to D300s to Dnext progression is making substantive, measurable leaps. Sensor size and performance, the addition of video, buffer capacity, in-camera processing, and a host of other things have all made substantive changes with each generation. So there's slightly more urge to upgrade amongst DSLR users than there was amongst SLR users. However, as I've pointed out previously, the gains are getting less tangible. Do you really need 16mp instead of 12? How often do you really need a 100 frame buffer? Are you really using the in-camera post processing capabilities? Or are you just taking pictures?
A lot of photographers dismiss the mirrorless cameras, but they form a pretty strong bridge between the small but less capable compact cameras and the big and highly capable DSLRs. As the answers to those questions in the last paragraph become "no, I don't need those additions" the next question becomes "well, would a smaller, just as capable camera be of interest?" The answer to that question will eventually be yes for a lot of the current DSLR upgrade crowd. For example, I use my Olympus E-P3 far more than my D3100. Curiously, the entry price in mirrorless is tending to be, you guessed it, US$599-699, somewhat the same range as the low-end DSLR. No wonder every camera maker (except for maybe Canon) wants into that market and for that market to eventually succeed: the price point is the same but the costs of producing the product is less. Profits are increased.
So prepare for more mirrorless cameras. As I've noted previously, it's been a mirrorless summer already (Olympus with three, Panasonic with two, Sony with three, Samsung with one new model announced and/or shipping). But don't prepare for the US$399 interchangeable lens camera. The camera makers haven't been pressured to get there yet. The price of entry is pretty much US$599, same as it ever was.