Usually the things that are reorderable in the Nook Shopping app are 1 TBT. The top hat and mask would fall into that category. Some DIYs are harder to come across than others (like right now the cherry blossom DIYs are dropping at low rates for people who already learned the recipes last year). The gold stuff I consider a regular DIY and 1-3 TBT is all I would pay for those. I hope this helps. I only needed about 50 DIYs when I joined the forum so prices might be more variable than I imagine.
Most people with lots of catalog items don't need in-game bells anymore. But a lot will trade for item variants (like me LOL!). I personally prefer trading because it is the only way to get the furniture variants unless you want to hunt down Wisp or shake trees until your arms fall off.
If you want to check if something is reorderable I have found the
Nook Exchange website helpful. If it is reorderable a little green leaf shows up in the lefthand corner.
