A 4k Netflix setup (with tolerance and overhead) will pull about 25mbs. so 3 TVs going would be 75mbs.
Unless you're downloading things 24/7 - 600mbs is in no way necessary for the average person - esp as the costs just keep rising.
That IS their whole marketing scheme - get the unaware users hooked on something completely over the top and then slowly raise the temperature of the water. Thats corporate 101.
I download ISO's, Windows updates, Steam files and other large files and my 100mbs service (dual WAN through TS) is perfect.