ehhhh, really depends on which CDN features you're using, and at what volume. Using ESI? VCL? Signed URLs or auth? Any other custom functionality? Are you depending on your provider's bot management features which are "CONTACT FOR PRICE" with other providers? Does your CDN provider have a special egress deal with your cloud provider?
It's possible to picture this being easy in the same way that being multi-cloud or multi-region is easy.