I use the following method for 2 reasons- 1) Keeps my Reagent Vendors Stocked. 2) Works out the cheapest way of obtaining.
How??
Get a rune book, go round and mark the location of every FACTION Reagent vendor, in most shards you will find @ 8 in each of the Faction run towns, if not, contact the Faction controlling the towns and request them placing faction vendors.
Then simply go round buying every reagent,
Its boring, & slow at first, but after an hour or so each one is selling you 999 lots of the 8 Regs @ 3 gp.
I did the math for my old guild and it was basically paying 1/2 the price of Vendor sold primers, and you had bulk regs to sell on @ double your money.
I found that spending an afternoon, @ 5 hrs I was able to obtain 2 Talismen, 1 pair of Wiz crystal Glasses and a plethora of resaleable @ double money regs.
IMHO...!!!