LLM summaries are basically free, its the TTS where the costs add up. Currently its ~.03 cents per episode. That is a number I've been happy with while running our beta testing. I found that power users were eating up nearly all or sometimes a tiny bit more than $5/month in costs but on average users were typically under that putting me in profit.
There is still a lot more optimizations that I have planned to bring that TTS cost down more. With scale I think I would buy out server space for running TTS models but at current volume API makes more sense and is not cost prohibitive to me.