Does cost reduction apply to Wayfarer’s changed cost? Or does Wayfarer’s text set exactly what the cost now is?
If during a turn nothing was gained yet, or only Wayfarers were gained, cost reducers behave as normal and apply to the $6 cost of Wayfarer.
If a non-Wayfarer card was gained, then the cost of that card is calculated (taking cost reducers into account), and it becomes the new cost for Wayfarer (which doesn't apply cost reducers in addition). The cost of the gained card is continuously monitored, and if it changes (say Canal was bought), so changes the cost of Wayfarer.
Of course, everything resets when the next turn comes around.