Who owns FX logic in your product, engineering, finance, or users?

I’m exploring a currency conversion API idea and trying to apply Lean Startup principles before committing to a direction.

So, I'm researching how different products handle multi-currency behavior and FX ownership, and I keep seeing teams split in a way that surprised me.

Some products treat exchange rates as core product logic because they directly affect pricing, balances, refunds, and user trust. Others push FX to finance, rely on daily accounting rates, or even let users input rates manually.

Before building further, I’m trying to understand:

• In your product, who actually owns FX behavior long-term?

• What made you choose that approach?

• Were there UX, trust, compliance, or operational reasons behind it?

I’m especially interested in real tradeoffs you’ve experienced, cases where the “obvious” approach later caused pain (or saved you).