I have one of the best 10VDC cal labs in the USA. In June, my master 732B was directly compared to Keysight's JJ array, with an uncertainty of 45nV. I have 7 Fluke 732 standards that are intercompared quarterly, and 6 calibration points on the master standard. For the last 3 years I estimated the output of the master before it went in for calibration, and all 3 years I was within 0.2ppm.
So, I can calibrate 10VDC to within +-0.3ppm. I'm charging $40 per for inexpensive standards that don't need to be shipped hot. No adjustments unless requested in writing, with traceable cert compliant to ISO 17025, to the original accuracy of device.
732B I charge $650. That includes 2nd day air return shipping. The customer is responsible to have a good battery installed, which will last for 72 hours according to Fluke. If the 732B is defective, the customer will be charged half the cost of the calibration, and return shipping will be cold (powered down). Certain things can be repaired. If a repair is possible, an estimate will be given, to be paid up front. Repairs are warranted for 90 days.