Heres what I tested...
vendor owner player 1 asks to see his vendors stock... vendor comes off porch, and his goods open. Adds item, but doesn't add price . (waits 60 seconds or so)
player 2 is standing nearby and opens same pack, tried to buy item and isnt allowed. says to wait 1 minute
After 60 seconds, player one (still not setting a price) sees item go to 999, but vendor hasnt returned to house/porch
player 2 is able to buy said item for 999 even tho item price hasnt been set,