If the two other people use the room, then they should pay the $50 each per night or, if you invited them, you should pay. Or, the four of you could split the total nightly rate.

<<I just wanted to know how prevalent the practice was, particularly for NYC hotels since they are ridiculously expensive, and whether hotel staffs generally will just overlook this practice.>>

It is common for hotels to charge for the third and fourth person. They use linens, towels, hot water, etc.

It would be more "riciculously expensive" for the other two people to pay for their own room.

If you were the owner/manager of a hotel, would you appreciate it if the employees "overlook" hotel policies and practices?