If you're going for 3.5" drives, then yes I can well believe that the sweet spot is with slightly larger drives, especially if you take enclosures into account. I did the calculations for work a while back for shoving hard drives into something from https://www.45drives.com/ and it seemed that getting the largest drives possible was the best price/capacity option.
Something that's easy to overlook with larger drives is that their rebuild times are worse.
"Shucking" drives throws the economics way off even if it means having to do some hacks and losing warranty... Usually the drives that come in enclosures are smaller.
A lot of ways to be efficient with money start by having or using a lot of it:)