This is basically a customer benefit for locking most if not all of their yearly day 1 game purchases in at BB. If a customer pre-orders/purchase a pre-set amount of games then once the final game purchase has cleared that added bonus is attached to that purchase.
A customer places 5 eligble titles into their shopping queue(say 5 of the current $10 pre-order titles) & once they pre-order/purchase all 5 the fifth game would recieve $60 in myBB points, $40 bonus for the previous 4 games & $20 for the final game(the reg. $10 + $10 bonus).
Maybe the # of games would need to increase to 10 resulting in $200 total credit or a possible way to allow all game pre-orders to recieve some credit compensation.
Either option is a huge financial committment to BB & $120 GCU, $300 or $600 annually, but BB has the benefit of larger pre-orders amounts which should equate to cheaper per unit orders.
Being able to advertise "EVERY NEW GAME IS $47.99 WITH $20 CREDIT" would completely remove key competitors in the gaming market. And the added affects on GCU with mybb points leading to non gaming sales & more active trade in volumes serves to strengthen the entire program. Also, this would be an equally potent benefit combined with 20% off there would no longer be any reason not ro fork over $120.
Wolfenstein pre-order numbers should provide insight to how strongly the lure of $20 credit with 20% can be.