Auto purchase stacks : "not enough money ..."

When trying to buy ammo I get the message "not enough money" while I have plenty of money to buy the required amount. Looks like the addon is always considering the NPC prices as unit prices and by doing so thinks that you 2000 bullets is 2000 times the price while it's 10 times the prices.

PS : same problem can occur with food (stacks of 5) if you are poor.