Maybe we can look at it at a different point of view. Maybe $2.10 is not expensive and bitcoin is worth a lot more. davidonpda calculated that using the AWS GPU cluster it would cost $150 per block. That means it would cost $3 to generate one bitcoin at this point in time. Therefore a bitcoin is worth $3.
If Amazon charges $2.1/hr then I would guess that this price is close to the "industry standard" in terms of cost for the hardware, hosting, electricity, etc., to be a profitable cloud computing company. That means today's bitcoin prices on the market are really cheap!