I've been doing the same-ish workload the past week (the graph shows the whole month), and it's been consistently on $10 USD/day.
Yesterday, however, spiked at $50 USD, and after just 2 hours of "activity" today, it's already at $10 USD.
What's going on?
Whatever is the darker shade of blue in the bottom-right graph had a bump at the same time cost did. Perhaps that's output tokens (which include reasoning)?
Using it daily for about 100%, and my monthly costs are about $40.
50/day is extraordinary, must be a billing glitch.