If you need extrapolation, you should read the TOS. It says you cannot use prime free shipping for items intended for resale. Buying an item to incorporate it into an item for resale is still buying for resale. If you buy items for resale, you're suppose to select a different non-prime shipping method.
It has nothing to do with the first sale doctrine. If you are reselling the item, then you owe Amazon shipping charges for 2-day shipping.
Maybe Amazon won't try to collect, but you have violated the contract you have with Amazon.. and they could come back to you later and send you a bill for all of the shipping charges you owe them. Maybe they won't do that.. if you want to risk it, that's up to you.
It has nothing to do with the first sale doctrine. If you are reselling the item, then you owe Amazon shipping charges for 2-day shipping.
Maybe Amazon won't try to collect, but you have violated the contract you have with Amazon.. and they could come back to you later and send you a bill for all of the shipping charges you owe them. Maybe they won't do that.. if you want to risk it, that's up to you.