Talk:RR3 Wiki:Upgrades Strategy For 100% Completion/@comment-2405:204:B185:8100:ECDE:8EF1:954E:3BC3-20180714115017/@comment-35867805-20180714122217

It's relatively straightforward:
 * The Performante needs fully upgrading for Supercar Clash
 * The cost of the upgrade is taken in Supercar Clash
 * So the margin for that series is 619-71 = -548
 * The Performante needs no further upgrades for the exclusive series
 * Therefore margin is 80.

All the rewards from a series are attributed the car that can complete the series. The fact you can get some of those rewards without completing the series is irrelevant to looking at the overall strategy.