For those who don't want to pay a premium for full frame, why not be thankful that good APS-C bodies are cheap instead of complaining that full frame bodies are expensive ?
I'd be fine with aps-c for the time being, but unfortunately aps-c is no equivalent alternative because the eos ecosystem is more geared toward ff - historically and marketing-wise. A lot of aps-c users who are ok with their sensor but want more sharpness or better lens build use ef lenses. While it is a strange side effect that ef lenses have an extended reach on aps-c, you can only use their full potential of on ff.
I find this a little perplexing because I agree that it's probably true for wide angle lenses, but it seems you only own tele lenses ? What is the extra potential you get from projecting your image onto a larger sensor with a tele ? If canon's long teles are capable of projecting an image onto a larger sensor still, does that mean that full frame doesn't use the lenses to their full potential either ?
Sensor technology hasn't changed substantially -- the 5DMkII sensor still costs much more to manufacture and is still worth much more (and performs vastly better than) a current crop sensor.
Well, it hasn't changed for Canon - that's what many people are complaining about :-p ...
No, hasn't changed period. Compare the SNR graph at DxO with any full frame model with the same for any APS-C mode.
but real question: How do you know ff the gap between ff and aps-c sensor manufacturing cost is as large as in the last years?
I don't know if the gap is as large. I do know that we don't have some Moore's law effect where sensors are improving performance along a sustained exponential curve. Many of the people who assume costs should be plummeting appeal to some kind of "Moore's law for cameras" but there is no empirical evidence to validate this.
But also, as I pointed out, manufacturing costs are largely beside the point (or at least only to the point to the extent to which they affect supply and demand).
The law of supply and demand states that if there's something that everyone wants that is in limited supply, it will cost you. If you're willing to buy the thing that is not especially rare, that most of the potential buyers have already bought, and some current owners are trying to get rid of, you can invariably get it cheaply regardless of how much it cost to manufacture (I suppose the 5DC probably cost more in real terms to manufacture than the 5DIII)
No matter how badly you might wish for it, you are not going to be able to get the latest and greatest toy with all the best and newest features for the same price as the old thing that nobody wants anymore. If the price on an item drops, it is always because the item has lost some of its shine, and at that point the complainers don't want it any more as they have found something newer and shinier to complain about.