Even with peering in place behind the scenes, cloud providers would still usually charge for egress from storage and cdn services to a provider like cloudflare.

Even with peering in place behind the scenes, cloud providers would still usually charge for egress from storage and cdn services to a provider like cloudflare. What Cloudflare et al are doing here is utilizing the peering connections that they have already in place and not billing at the usual egress rate when traffic routes over these peering connections.