GC seal items like coke and hardened sap and such are still quite valuable. Submarines need vast quantities of them (81 for any given stage of creation due to things like Galvanized Garlond Steel calling for 9 cokes per recipe, or Cryptomeria Lumber and its 9 hardened saps) - and not everyone is patient enough to wait until they've got their own seals for those items.

So yeah.
  1. Turn your poetics into gear.
  2. Turn gear into GC seals.
  3. Turn GC seals into coke.
  4. Sell coke on the market boards.
  5. ???? (time)
  6. PROFIT!