Caching has so many caveats. The cache expiration window is short, if you change document in the context it clears the cache, if you change anything in the prompt prefix it clears the cache. And there’s no reason to think that Anthropic will keep charging dramatically less for cached tokens on the future once they start trying to make a profit.
Yeah of course they do because it saves them more money than they are passing on to you. That doesn’t mean that they are magically able to overcome the tradeoffs inherent to caching. All of the issues I mentioned will still invalidate your cache.
keep in mind that those 50k memory tokens would likely be cached after the first run and thus significantly cheaper