What you are paying for is what you usually pay for: convenience and consistency. When you send a print job off to the printer, you tell the printer what you expect to see. For many years, the easiest way, for solid spot colors, was specify the Pantone color. You knew what you were looking at in your office was what the press operator was seeing. But it does seem like in these days when reliable digital color calibration tools are available at affordable prices, that it would be easier to not rely on the Pantone color books, at least for anything that could be spec'd in standard CMYK.