Due to the Backend Service cost, including APIs' fees & Cloud Service fees, etc. Udemy Dual Subtitles needs to charge a small monthly fee to cover the bill.
Actually, this monthly price is relatively small compared to what would cost if you use these Service yourself. And we've avoid many pitfalls for you.
What we've done for you?
Briefly, we maximize the utilization of the services.
1. load balance service usage
2. cache translation results to avoid repeat API calls