Summary of my Hong Kong tailor doing business on US trips:

Customer:
International txn fee:  2-5%

Merchant:
Processing fees:  4%
2.5% exchange rate from us card swipe to HKDollar bank account
3-4 day settlement to HK bank acct (can't directly spend in US)
Must use AMEX on US trips, so 19% interest on all expenditures

Founder, Market Research Edge:
CoFounder, MyBackpack:

Dad bod.  Bulldogs.  Trophy husband.

These fees are so cheap...only 6.5% - it's the 3-4 day settlement to HK bank account that is the bullshit.