This reddit thread¹ details thoroughly the connection to Meta (Facebook) and to a lesser extent Discord as being behind the push in the US.
1. https://old.reddit.com/r/linux/comments/1rshc1f/i_traced_2_b...
The marginal cost of one extra passenger is going to be very nearly zero. The vast majority of the cost is just moving the bus / train / plane, and the overhead / inefficiencies in the system. I've seen somewhere the numbers for one passenger on trains and planes but I can't remember where that was. Just know it is a very very small amount for the added weight of one more passenger.