My favourite auto-vendor event was with a 3rd party addon, ATSW (advanced tradeskill window). My 70 rogue main at the time was an alchemist. I needed to buy the vials that were 5g a stack to make some potions. ATSW would conveniently auto-buy what you need when you opened an appropriate vendor.

My inventory (3x18 slot bag, 1x 20 - back in TBC days) was almost completely empty - I like clean bags.


I open the vendor, and to my horror it bought as many vials as it could to fill the bags. It ran out of gold shortly before filling the bags (I wasn't too rich, only had in the hundreds of gold on the toon). Then I had to vendor them back at quarter-price...didn't want to fillout a GM ticket as I figured they'd wave the "ADDON! ADDON!" wand and say I'm screwed. I did have to vendor most of them back, I didn't even have enough gold to post the auctions of the potions I made with the vials I actually needed <blush>