For fun, instead of buying a stack for 2500 platinum each in the bazaar, I figured... hey, maybe I should actually put my already-maxed pottery skill to use and make them myself, see how much I can save.
Gathered enough materials for 20 seal combines by vendor, farmed the dropped items myself or had them in bank already. It came to approximately 17920 platinum (didn't add gold, silver, copper costs so it would be a tad bit higher). That's about 900 platinum per success. Bulk of the costs came from needing 100 rubies, holy crap.
Of course I wasn't lucky to make all twenty, only thirteen, but that still saved me a chunk of money.