I don't see this doing much for a gold sink, prices like these will only hurt people who are low on gold and will have no effect on rich characters.
This is why I think a tariff system (while more complex) would be better.
Besides the reasons I listed previously, I'll also add that even the Vistani might have a rule similar to airlines: one carry on, or otherwise you pay extra! Seriously, transporting stuff--not just people--costs you more.
Going farther and to more dangerous areas makes sense to charge more, too, but a lean traveller should pay less than someone who is heavily laden, the Vistani can see is wealthy, is hauling local riches out of a realm, or is bringing into a realm goods that would compete with the local merchants. Free international trade is a pretty anachronistic concept to have in the Mists.
and Another idea is that the npc healers only offer free healing to a pc only once a day and charge money if you want to be healed more often. (with the added benefit that people seek out pc healers more often)
+1
Another idea I had would be to have you be able to rent servants in Port a lucine (and mabye even buy slaves in Hazlan or Har'Akir.) These would be non-combat henchman with mostly a status function and maybe a limited carrying capacity. They would not follow you outside Port or into dangerous locations.
This opens up a lot of possibilities IMO. This would be more interesting than the ever-present oxen
At least for those who are not slaves, perhaps if you get one killed you must pay to have them resurrected. If you don't, the others decline to work for you from then on.