Yes, I'm really not sure either. All the stuff you're putting in bold talks about bitrate, i.e. memory taken on a storage device or bandwidth needed for transfering over a network.
Neither is what anyone was talking about. I think we know pretty well how much MP3 encoded audio fits in a SD card, as well as how much (less, obviously) fits as 44KHz, 16bit encoded.
Decoding PCM data involves reading a word and feeding it to the D/A.
Decoding MP3 involves taking Fourier transforms and things like that.
If you need a proof that the latter is more computationally intensive, well, I'm not sure I know of a place that can has it - I generally don't Google for completely obvious things.