Hot take: the $60 comic size hard case I bought at a con in Lansing beat every cardboard box I've owned
Dropped 60 bucks on a hard plastic case with foam padding at a small con in Lansing about 8 months back. I figured it was too much for what it is. Then my basement got some water in it during a storm and the two longboxes on the floor soaked through. Keys, a couple of nice covers, all wavy. The case was sitting right next to them on the same shelf and everything inside was bone dry.
So the cardboard burned me for maybe $200 in damage and the case saved me for $60. Bit of a no brainer in hindsight. What's the rest of you using for the stuff you actually care about?