Have I been ripped off?

RonJG wrote:

Just bought an SD1M and am disappointed with image size.

I was informed that the image size from the SD1M was 46mp. That cannot be because when I take a jpg and display it to fill my 27" screen, it is at 77% enlargment

Nikon D800 at full screen is only 34% enlargement.

I also noticed the Sigma images are only 180 dpi whereas the Nikon ones are 300 dpi.

Am I doing something wrong here or is the advertising duff?