It seems the answer for Cloudflare is that the real price of their services is just a lot more hidden.
9 cents per GB is still a lot more than it needs to be. It's a form of vendor lock-in. BunnyCDN charges[1] 1 to 6 cents per GB depending on the region, or 0.5 cents and lower for the "volume network" with fewer POPs. They've done so for years, and it funded their entire operation until their first investment round last October.