Yes, I discover this too just now. In fact the mega gold also didn't work.
Is the game got updated recently? or what could have cause this?
I sell the item to merchant but when I buy it back, it came with the original amount of 1, although it should be 99.
Then you are doing something wrong.
Press the key, then FIRST open the inventory, ingredients should all be set to 99.
Go to a vendor, sell everything. Turn option off.
Buy everything back.