I wonder what the cost is compared to terminating SSL at Clodfront? For my web tier architectures, I use Cloudfront to reverse proxy both dynamic content (from the api) and static content (from s3). SSL is terminated only at CloudFront.
So for 10k HTTPS requests, the price is 0.01 $. If you serve 5 billion per day, that is 5000$ a day. With such high traffic I believe it is needed to handle it using performant webservers (Go, Erlang?) to keep costs reasonable, and probably terminating SSL at load balancer is the way to go