Bands and event organisers who add bandanas to a merch table are usually surprised by how well they do. There are four unglamorous reasons.
No sizing, no dead stock
A shirt run means guessing a size curve, and every wrong guess is stock you carry for a year. A bandana is one size, so the entire order is sellable and the leftovers go straight onto the next date.
That alone changes the risk profile of the table.
The impulse price point
It sits below the threshold where people stop to think, which means it sells to the crowd who would never queue for a shirt — and it sells as a second item to people who already bought one.
It gets worn at the event
A shirt bought at a show goes into a bag. A bandana goes onto a head immediately, and then several hundred people are wearing your artwork in front of everyone else for the rest of the night.
No other merchandise item does that.
Photographs well, travels flat
It packs into almost no space, ships cheaply between dates, and shows up in the crowd photographs that end up online. Merchandise that is visible in the documentation of an event keeps working after it.
How to run it properly
Two designs, not six. One flat-colour screen print at volume for the table, and, if the audience supports it, one tie-dye or embroidered run priced higher for the people who want something nobody else has.
Order both together, and keep the artwork on file so a reorder mid-tour is a single email.