You cannot convert a Glock or make a machinegun. Congress cutoff the new registration of machineguns for civilian possession in May 1986. CQBArms can do only because he is a licensed manufacturer, and even then its just a LE sales sample that will have to be sold or destroyed if/when he ever gives up his license.
The cost to him as a licensed manufacturer? Whatever the cost of the G17 and making or buying the conversion part, the manufacturers FFL (07), the SOT ($500/year), the state department's ITAR fee ($1750/year), a facility or premises that is zoned industrial (or has zoning not in conflict with manufacturing), the cost of all necessary state and local business licenses, and the time and effort of making it a bonafide business (because just obtaining an FFL/SOT just to enhance your personal collection can result in BATF rescinding the FFL/SOT and seeking charges of tax evasion, perjury, etc.). Of course, if you just wanted to buy it as a licensed manufacturer/dealer you'd also need aan official request for a demonstration of the weaponn in question by a LE agency just to purchase it.