You bring up a valid point, and indeed the cost math doesn't add up at the moment. My argument is that if you are an e-wallet provider specializing in Vietname

You bring up a valid point, and indeed the cost math doesn't add up at the moment. My argument is that if you are an e-wallet provider specializing in Vietnamese Dong, then implementing a Bitcoin wallet into your existing offerings is trivial, since most of the required technology stack is open-source. If you are an e-wallet provider specializing in Indonesian Rupiah, implementing a Bitcoin wallet into your existing offerings is also trivial. The magic (and cost reductions) will come when users realize these silos can now talk to each other. I believe it's a question of why not? instead of why?