How come a language learning wrapper costs WAY less?

I used to use chat gpt for spanish learning. It was great for a while, but I kept hitting the Advanced Voice usage wall on the Plus tier. If you want to reach real fluency improvement, you need at least an hour of speaking practice a day. On the Plus tier, that is impossible. To get unlimited voice natively, OpenAI wants $2,400 a year for the Pro tier. I did the math on the Realtime API too. At $0.30 per minute (the blended rate for audio input and output), 60 minutes a day for a year costs about $6,570.