Thats what the difficulty adjustment is meant to do. The inflation rate is kept constant. And thus further proves the point that difficulty has got nothing to do with exchange rates. The supply unrolls in a fixed expected rate. What was meant by 'fixed'. However the exchange rate is driven by demand.
So your thesis is that the fact that it takes $8.6M worth of computer equipment running maybe around 5.4MW to generate 300 btc in an hour has no bearing on the price than if it were just a $100 computer with a $56 card running at 60W. Sounds logical to me!
Or maybe, just maybe,
it's all related.
(numbers based on 9603.45 GH/s, $900/GH, .56 KW/GH)