Here's a good article on sensor sizes, and how it impacts all aspects of your picture - it includes interactive DoF calculations, focal length multipliers, and diffraction effects.
Here is what it says about sensor cost.
The cost of a digital sensor rises dramatically as its area increases. This means that a sensor with twice the area will cost more than twice as much, so you are effectively paying more per unit "sensor real estate" as you move to larger sizes.
http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm
I will hereby refer to 4/3 cameras as the "4/3 racket". Here's my belief. Increased competition and a flooded DSLR market leads to shrinking margins on prosumer/enthusiast cameras. Manufactors are seeking ways to improve margins by decreasing the production costs of their products, while
increasing price. How to do this?
1. Reduce the cost of production by shrinking what matters most in terms of IQ in a digital camera body, and also costs the most to produce - its sensor. Sensor size effects:
A. Diffraction
B. Noise levels at higher ISO
C. Dynamic Range
D. Lens crop factors
2. And while we're at it, let's get rid of the next most expensive thing - the optical viewfinder, so you have to hold your arm out to frame and replace it with a cheaper to produce LCD (just like a cheap point-n-shoot...). (How is it that the many of the same users who tout, and pay a premium for, the excellent rangefinders in Leica are satisfied with
just an LCD?) I can just hear the meetings in Oly's marketing department -
In fact, "JB", while we're at it we can sucker these "enthusiasts" to pay even
more by charging a premium for a viewfinder hotshoe accessory!
So, how do you get people to buy into this? Take a page from auto manufacturers... (In fact, this whole thing is copped from the auto industry...) Make the camera
look cool! Yeah, give it a "cute" retrto design! Clean lines, now that we've gotten rid of the unsightly "hump" that houses the prism - and while we're at it, let's get rid of the flash too! Yeah! So, if these "enthusiasts" wanna use a flash? They have to buy
another accessory. Cheap out on the innards, make the camera look cool. Want other basic features other less expensive cameras have? It's an "accessory". All ala carte... (Make sure we have a Leica lens adapter ready before we go to market... heh, heh - wink...)
Well, nice racket was the 4/3rds game, while it lasted. At least EVIL cameras pass the lower production costs for what they leave out on to the consumer
and don't skimp on the sensor size. APS-C is
already a compromise over full frame. And, post all the pics you like, compact DSLRS are larger than 4/3 (because they have viewfinders, larger sensors, built-in flashes...etc) but the newer ones are well-designed, have good ergonomics, and their larger size with a prime lens is simply not enough to matter in any meaningful way.
As Ric Flair used to say, "...that's just the way it is, learn to love it. Wooooo!"
EDIT: Do note that with compact DSLRs, competition is causing
more features to be included with the camera (like swivel screens) for
less money with technology from higher end models being pushed downward. More for less... Not the case with 4/3... well maybe we'll see some of that now that the 4/3 racket has been exposed... It's hilarious that those who criticize entry-level DSLR models b-tch about them not "having enough buttons" and having to rely more on menus (a reasonable compromise to keep costs down...), will run off and buy a considerably more expensive 4/3 camera
with a significantly smaller sensor and
no viewfinder and
no flash...