Reducing the cost of a custom system isn't irrational. My own personal budget is very limited, buying two IronWolf HDDs in this case is easily a good chunk of

Reducing the cost of a custom system isn't irrational. My own personal budget is very limited, buying two IronWolf HDDs in this case is easily a good chunk of my monthly income. If I can build a NAS that can expand with single drives as needed, it's more cost effective for me. And I imagine a lot of others have the same problem. In the end, by buying 2 drives when a single drive could have solved the problem equally well: expanding your space by 4TB, is wasting money. Period.