This is just my opinion, but I don't think most members of the general public would be interested in buying typical team t-shirts. There are a variety of reasons I can think of:
1. No connection to the program. Everyone on CD knows what a ThunderChicken is, but to most people it's just a chicken head on a shirt.
2. The walking billboard look. Most team shirts are plastered with sponsors on one side, the only time I've noticed people with shirts like that is free shirts from fundraising causes (Race for the Cure, Relay for Life, etc.). I guess robotics shirts could fit into that same niche, since they could be sold as a fundraiser...
3. Cost. Most team shirts are printed in small batches, which drives the prices up into the $10-$15 per shirt range. If you can't get shirts donated that would require charging close to $20 per shirt to use them as a fundraiser.
I would expect a handful of shirts to sell well, but most would need an overhaul on how they are laid out, the color scheme, and the logo (if the team even uses one consistently). If teams made shirts that "fit" with other common shirt designs there could be a market. Back when 498 was named the Armor Plated Serpentines I had a guy at Panda Express mistake my team shirt for a heavy metal band, maybe I could have sold it to him
