Cloudflare is a default choice if you want to pay as you grow bigger and get a free SSL certificate.
However, you can get one from Lets Encrypt, and don't forget to reassess your decision when your situation changes - your users consume more traffic and services from a content delivery networks.
Bigger organizations may benefit from Akamai's pricing if an assigned sales executive would be hungry for new business.
Want to check your upgraded API and DDoS resilience defenses? Check our API penetration testing service
and DDoS resilience testing