As a former subscriber to Comcast (I moved out of their area, and now I'm stuck with Charter's bullshit instead), I can at least confirm that the 300GB data cap they list is actually 300 gigabytes, as it reads. I frequently crossed it on my 50up/10down gbps connection, but they were not enforcing the cap at the time, and my router's logs (I have and had an ASUS RT-AC66U, behind my own Motorola Surfboard modem) agreed with Comcast's. I do wonder how accurate OP's router logs are. I normally wouldn't have any doubts that Charter was overcounting (and 800GB seems excessive even considering the following concern), but my household crossed 300GB regularly with only two users, and habits similar to those described by OP. If his logs are showing only 150GB with more users, then I have a hard time trusting those logs.