How do you figure out which OpenAI usage is worth the cost?

We’ve gotten to the point where just looking at our total OpenAI spend every month doesn’t tell me much anymore since some of the increase is completely fine because we’re simply doing more with it but there are also workflows using larger models, longer context and way more tokens than others then you have retries and agent runs where the cost of one task can vary quite a bit depending on what happens along the way.

Seeing that we spent more this month than last month isn't really enough to tell me whether usage is getting better or just more expensive and I’m starting to think we need to look at this closer to the workflow level and compare what the tokens are actually accomplishing instead of treating all OpenAI usage as one bill.

If any of you guys are running a decent amount through the API. What are you actually tracking? Cost per workflow/task, tokens per successful run, spend by team/project, retries, model usage or something else cause I'm trying to work out what metrics are useful before we build a bunch of reporting that doesn't get looked at.