The problem with buying it from the wards is:
The wards are empty o.o. There was a 12 hour period where there were no sales, and less than 20 crystals available (2 were at max price!)

I got lucky and just kept checking the wards and finally found someone who put some up, and right away bought them.

(This is what prompted this question. When the wards are empty again, I have no realistic course of action but to enlist the aid of a friendly alchemist... then lock them up in a room for several hours and make them make me stacks of crystals).

Just wanted to make sure I did not miss an obvious/easy alternative that I never realized ^.^;