Do low level equipment writs on a high level character. You get scaled gold and exp, and the mats are much cheaper, plus a stack of mats goes a long way with an L1 or L2 level writ.
- Farm and sell alchemy mats. Harder to do without a guild trader but still possible.
- Level up legerdemain and thieves guild, then steal and fence as many high quality items as you can in a day.
- Quest and vendor everything, seriously you'll end up with quite a bank account doing this.
- Steal enormous amounts of provisioning ingredients (easy to do around the docks in big cities), craft a bunch of food (with the 4x provisioning passives) then vendor it.
- Farm rare motifs and sell them (again harder without a guild trader).
Probably more I'm not thinking of...