The biggest chunk is the bandwidth charges from imgix. They do appear to be giving you a break on their published pricing, but not a huge one ($0.075/GB vs $0.08/GB). The CDN they are using appears to be Fastly, which also has a published price of $0.08/GB. So, there doesn't appear to be any overzealous markup on imgix's part.
At your scale, there are CDN providers that can get down to $0.05/GB or lower. That would cut your bill by $3500/month...roughly 20% lower than current. I assume moving your legacy CDN stuff at the same time might add to that savings.
Not sure how tightly bound imgix is to fastly, if fastly has some feature that's not available elsewhere, or if imgix would even be willing to entertain support for alternative CDNs.
Edit: Also curious if you've ever done any analysis to see if bots are using a significant portion of your bandwidth. High res images sounds like a popular target for leechy bots...maybe some savings to be had in detecting/blocking that?
At your scale, there are CDN providers that can get down to $0.05/GB or lower. That would cut your bill by $3500/month...roughly 20% lower than current. I assume moving your legacy CDN stuff at the same time might add to that savings.
Not sure how tightly bound imgix is to fastly, if fastly has some feature that's not available elsewhere, or if imgix would even be willing to entertain support for alternative CDNs.
Edit: Also curious if you've ever done any analysis to see if bots are using a significant portion of your bandwidth. High res images sounds like a popular target for leechy bots...maybe some savings to be had in detecting/blocking that?