I suspect that the sheer costs of everything everywhere play a part in the costs of ADDA, interfaces, and such. Someone (be it California or China) has encode, build, assemble, package, and ship these things, meaning payrolls, health insurance, all that stuff. Facilities like rent/mortgages, the costs of keep the lights on, heating and cooling, corporate insurances, and such also have gone up, costs not directly tied to the price of chipsets. Businesses have to pay taxes, rates that vary wildly, depending on locale, as well as advertising (which have seen their own rate explosions).
Each 3rd party involved in getting a product from raw materials to your desktop/studio racks also has to offset the costs of reality on to you and I just to stay in business. As Craig so eloquently outlined, the actuality parts components involved in non-digital support of said chips is also pretty dang important in all this, components meant to last decades, not weeks.
When considering everything involved, I don't feel so 'ripped off' anymore...and considering how a $300 interface now can outgun a $3000 from not so long ago, I'd suggest we are getting a lot more than a bargain. Anyone remember Digidesign's completely proprietary HD line?