Your link doesn't work, this one does: http://www.finiki.org/wiki/Norberts_Gambit
This might well be what someone like Travelwise is doing on the backend, especially if they have the volume to offset the commissions.
The HN markdown parser is stripping the apostrophe in both of your links. Try this: http://www.finiki.org/wiki/Norbert%27s_Gambit
More information here: http://www.finiki.org/index.php?title=Norberts_Gambit