Board Thread:Game Discussion/@comment-31526827-20171030020306/@comment-26829117-20171031150727

Had you bought the FXX-K then your rewards would have been 100, 0, 0, 0 = 100, not 25. However, the opportunity cost lost would be 600 in this example as you can't get 100 reward again for another three weeks even if you have the next three cars fully upgraded.
 * Week 1 - Group B - 100
 * Week 2 - No Car - 0
 * Week 3 - No Car - 0
 * Week 4 - No Car - 0
 * Week 5 - Group B - 0 (Week 2/3/4 no car)
 * Week 6 - Group B - 0 (Week 3/4 no car)
 * Week 7 - Group B - 0 (Week 4 no car)
 * Week 8 - Group B - 100

Maintaining Group B eventually pays for itself as the same cars keep coming around. However, it is much easier once you have a full garage and even easier than that once you reach 100% completion.