The 400 Shekel Kesef:
There exist 400 worlds of Divine pleasure which the Tzadikim will inherit in the future. These 400 levels of Taanug/pleasure were represented in the 400 Shekel Kesef that Avraham gave when he purchased the Cave of Machpelah for Sarah’s burial from Efron. These 400 spiritual levels of G-dly pleasure were then used by Efron to fuel Kelipa/evil. Eisav who came to Yaakov with 400 men represented the 400 harsh severities that were created from these coins given to Efron. The reason why Avraham gave these coins with their spiritual representation to Efron is to invest them into Kelipa and then reap from it a much larger section of Kedusha.
 Torah Or Vayishlach 24b