How do you define "extremely expensive"? CloudFlare's Business Plan ($200/mo) includes advanced DDoS mitigation: https://www.cloudflare.com/ddos/.
Also, due to caching of assets in PoPs close to end-users (and TLS termination at the edge), the site is often much faster than without DDoS protection.
Also, due to caching of assets in PoPs close to end-users (and TLS termination at the edge), the site is often much faster than without DDoS protection.