yes that is one use case of digital assets like BTC: converting any international money transfer to a domestic money transfer, greatly reducing compliance flags, time and possibilities of banking errors that no bank wants to be accountable for and figure out themselves. often times leaving no record in payment networks like SWIFT, because only two local payment networks were used, one in their respective monetary union.
the cost is 100% tied to liquidity of that market. the bigger and deeper the market, the lower the transaction cost.
It is more likely that HKD's bitcoin market would be less liquid than USD's bitcoin market, so you would want your bank in Hong Kong to accept a USD deposit from a local OTC broker, and then convert to HKD at that point if you wanted or needed it.
