Ticket prices for my group members are different, even though we make reservation together.
We have "First Comer Discount" for buses operated by Willer Express/Star Express.
The very first passenger get the cheapest price.
The next passenger get cheaper price than normal price.
After that the price will keep increasing until it reaches normal price.
If you book for many passengers at the same time, the price will increase gradually from the first member to the last member, until it reaches normal price.