I'm willing to bet for a price of $299, they are only calibrating the DVD input and the sound system. I'm also willing to bet it doesn't include any adjustments within the service menu. This would be necessary if you want the customer's default settings to be the calibrated settings. The $500 price sound more like the cost of a full calibration, which usually runs approx. $165/input. To me BB calibration is better than nothing at all, but shouldn't be labeled an ISF calibration.
I've been through ISF calibration classes and own a Sencore P403 video signal generator. I've performed many calibrations and feel it's necessary to use the service menu. If the default setting are not the calibrated settings, the customer, their children, or friends can change the settings and unless they're recorded, will require reclaibration.
I'm not sure how they would be able to adjust to D6500 without a sensor to determine the correct proportions of RGB.
Probably for the general public, their calibration is of value as long as they include the satellite/cable input. What usually happens is people get so used to the "Torch Mode" set by the manufacturer, correct calibration tends to look dull, so they end up changing the setting anyway.