Does that new architecture make it more expensive to serve worker’s static assets and do worker-to-worker invocations? Or just harder to measure?

This change in billing makes enabling caching not such a straightforward decision, and encourages separating cached and non-cached parts of your workers into two separate workers, which is a bit annoying.

I wasn't personally involved in pricing here so I can't really say exactly why it is the way it is.

However, I'd note that, in terms of our costs, it's often cheaper for us to run your Worker than to serve from cache. Consider that Workers run locally in whatever edge location the request landed in. We are not saving any bandwidth costs by putting the cache in front of Workers rather than behind, and we've built an architecture such that running a Worker is extremely cheap, almost free.

In that light, making cache hits free would basically be giving away money. To be honest, that is another reason why implementing cache in front of Workers has been held back so long. I think the team finally decided that the only way we can deliver it without giving away too much money is to charge full price for the requests. Workers pricing is already incredibly generous, and we do need to run a business at the end of the day.

(Of course, a cache hit still saves you the CPU pricing. CPU time pricing more directly translates to costs for us, so that makes sense.)

I admit the side effect on static assets is a little weird. But no other provider offers unlimited free static asset serving to start with -- so it's only weird relative to our own unreasonable standards. :) I think the thought here is that if you need caching in front of Workers, that implies you are doing complex work in Workers and getting a lot of value out of them. So a bit of "price segmentation" kicks in here. That said, you can work around it by serving static assets from another hostname, etc.