You’re correct that every passenger on the same PNR will have the same price for the ticket.

You’ll never know the impact of booking a ticket until you actually do it (or at least put it on hold). Only then will you be able to see the pricing for any subsequent ticket(s) you want to book.

Just because it says 7.5k if you search for 1 pax, and 9k if you search for 2 pax, doesn’t necessarily mean that after you book one pax at 7.5k, if you go to book one more it will be 9k (or 10.5k or any other number you previously saw).

There are also very recent examples where AA has filed fares that offer lower pricing if booking for two or more passengers, and higher fares if booking for just one passenger. These examples were on the cash side, but there is no reason similar rule conditions can’t be applied on the award side too.