What is the definition of a costly material component - Spells or infusions with a costly material component, a costly focus, or an XP cost cannot be stored in a minor schema.
My off-the-cuff answer without looking it up:
Look to the Eschew Materials [Metamagic] feat, which is 1gp or less, IIRC.
So costly would be more than 1gp.
Yea, that is a good start but at low level the term "costly material component" would be the pearl 100 gp, but at 10th, that is chump change and would not be a costly material component
found one website with this; If the spell lists a material but no cost for the material, then the material is assumed to be very inexpensive, fits better unless you have a corner on the market say bat guano costing 100 gp per pinch
