People come to the WT for Healing, etc. I'm sure they would donate what they could for that. (When Verin and the girls returned to TV with the HoV, people were lined up waiting to get in, IIRC)

With the ability to create cuendillar, they have something of value they can sell to those that have money to spend. (I recall Egwene pondering this when the rebel AS were running short on funds.)