to me, the rarity of the vehicle plays an important part of the whole numbers game.
like if i was gonna buy an M code car it would have to have the #'s matching motor and trans. the same for something like a survivor car or a "1 of [***]" piece. that, to me, is what makes it special and unique.
on an S car, non OG numbers but correct pieces would be acceptable with that type of 10~15% adjustment. again, in my personal thinking. it wouldn't be a deal breaker, but the number could move the needle either way if i was on the fence.