If Kimi doesn't race F1 next season it is very likely that his value will go down significantly. And, as for the guys who win the 17 or so races up for grabs next season? Well, their values will go up.
If Kimi is concerned about money he best race next season. So what if he "loses" 2 million by racing--he stands to win races (and increase or maintain his market value) if he continues with Brawn.