I paid for it about 4 or 5 years ago to use on my first smart phone, a Samsung Galaxy S and at that time, had Unlimited Data plan.
I doubt that subscription is valid anymore.... and I have not even tried to use it on my S5....
I don't use enough data to even begin to worry about exceeding my 3 gB data plan...
but, I am not tethering a laptop off of it either. I do that at night from a motel or other WiFi hotspot IF out and not at home.
At home, I have ADSL 11.5 mB downlink, 500 kB uplink for my desktop PC.
My Verizon cellphone walks circles around my AT&T ADSL connection, but I can't afford to use that much data all the time via VZW. so, I crawl along on the ADSL connection.