For batch processing only. Make them cost 20m each or something ridiculous for a tool, and when processing stuff that requires multiples of a mat to work, they have to be individually separated stacks. The process time could be cut by 25%, but it still has to go through the same amount of cycles you'd normally be required to do, to get through the stack(s).
Ex:
{
Double Boiler
Cost: 19,999,999(9,999,999)
Rarity: Legendary
Prereq: Level 75 brewing, Courage, and Knowledge
Tool Type: Oil Production
Right Click for Option to Use
A highly efficient, portable way to extract oils from vegetables and fish.
(must use 2 equal stacks of veggies and 1 stack of fish per use)
}