You can't avoid this. It is either your client or bank's client. And no bank will take the burden to account every $0.2 transaction for you, spending its own computing power. It just a quite expensive thing to do. That is why banks often separate the main ledger and retail ledger[s]. Each system tuned for a different performance profile.

One should not build their own cryptography, one should not build their own ledger, that's what I am saying.

I've seen a lot of ledgers. Crypto is much more complicated.

In the end of the day you provide a full stack or just do UI/marketing. This is a good old vertical integration dilemma.