This skill is being pushed to obsolescence within the game. Recipes need to be retconned for consistency or the skill needs to be removed, as its completely unclear what its intended uses are in the game going forward.
Originally, high tiered invention epics had no such restriction for the skill. Meaning high profit margins could be made when the skill activates on expensive components. This seemed to reinforce the original intentions of the skill.
Now we get to the newer epics, including the tiered versions, which all exclude the skill from being activated. I guess the intent has changed to remove the skill from being able to save highly expensive items, in order to keep them rare and sought after for the sake of game economy. So maybe inventor 2 is only supposed to be used as a quality-of-life buff for inventing low rarity items and potions, like saving the odd bloodbloom extract every now and again? This would be fine, if it was consistent between 'high value' recipes; but as we can see, that is not the case.
NOPE! It seems even something as ubiquitous as bard extracts is out of the range for the likes of inventor 2. So, what is the purpose of this skill in the game's future? All new recipes seem to carry this restriction. There needs to be clear consistency or intent behind these restrictions. Otherwise, the buff simply doesn't have a place in the game. I'm actually shocked this buff is still allowed to activate on thieves' guild event recipes; maybe that's the only home for this poor skill.