Weiß nicht, ob die Information noch jemandem nützt, aber laut jüngstem Update kann man die Gruppenpledges auch einfach erweitern und der Einzelpreis pro Spiel bleibt auf dem 6er-Gruppen-Niveau:
If you are part of a larger group and are already at the six games pledge level, you can add additional games by adding $40 per game (US) or $50 per game (international). So, for example, if you were in Australia and wanted 8 games total, you would use the six games pledge (which is $300 with international shipping) and then update your pledge to $400 so I know that you actually want eight games.