Just the glass, not the digitizer? I've seen prices around US$40 just for the part. Figure at least that, and maybe double that, for the labor, and more money for some profit. If it's the digitizer too, they run from about US$179 to US$225, depending on where you look - for the part.
My co-worker lost his S6 (forgot it in a taxi in NYC) and had to get it replaced by Asurion who was kind enough to give him an S6 Edge, next day it slips off his counter and cracks the display in 4 places, not pretty. He was told $250 to get it replaced. I told him to get a case and a tempered glass screen protector to at least help minimize the damage.
For any of those that are still wondering the cost, my S6 edge is being sent in to Samsung to repair the glass. The phone doesn't have a screen protector, but I did have it in a protective case that has a rubber bumper on it. It has fallen multiple times and nothing has happened to it. But lo and behold, the screen cracked while in my pocket!! Its just a hairline crack running from the upper right corner across the device and ends halfway down the phone. I have no idea how it happened. I always repair my phones so I decided to go with no insurance route. Not only is the repair tedious, but no real replacement options out there yet. I had to shell out 237.01 for the repair. The turnaround is about 5-7 days because there are no walk-in repair centers here in Chicago. Have to ship it all the way out to Texas. I'm choking this up to the stars and planets aligning.... what a bummer.