I have quite a few friends who are into sword fighting. There are hundreds of people who gather at the park every weekend and thousands who participate in week-long LARP's. They build their own swords and other weapons out of foam over PVC piping or fiberglass rods. Most of the time, they're made from foam camping mats cut into strips and glued to the rods and then covered in duct tape.
There's a niche market for molded foam weapons, but they're usually made out of latex and tend to be very expensive. Latex weapons tend to go for $75 or more for standard shapes and up to double that for custom shapes whereas the ones made from camping mats cost about $20 to build. Also, homemade ones are much more resilient, so most people who do own molded weapons tend to only use them at major events for fear of damaging them and not being able to show them off.
Needless to say 99% of the weapons seen are the homemade mats-and-tape variety. If I could drop the cost of standard molded weapons to $40 or less, they would sell like hotcakes.
Personally, the battles aren't my thing, but I would still love to profit from them
