Contrary to what Hollywood and the internet would have you believe, not everything is a conspiracy. Inventing conspiracies any time something doesn't meet your worldview is just plain lazy.

As for providing the hard data, if that's what you're after, subscribe to the Wall Street Journal.

This is NPR. It's a radio network. It produces radio-sized reports. It just happens to also put those reports in text form on the web as a convenience.

It's great that you're interested in the data. Go find it. It's out there. NPR isn't going to hand it to you on a silver platter. That's not what NPR is for. That's not what radio is for.

Whoever is gathering supermarket pricing data on a nationwide basis

The federal government does this every month. The data is available. Go nuts.