A bogus host will obviously not respond to the RST but the last router-hop that receives the RST will (per RFC/protocol specs). The response is destination unreachable via ICMP. The ICMP unreachable packet is cheap (non-persistent) and requires no up-keep from the last hop to the bogus host. Most importantly, the ICMP unreachable packet requires no upkeep from the filtering node in EC2.

Regards