With the greatest respect the Norfolk and Sufffolk Broads are the result of investment over hundreds of years. The EA, all the councils, central Goverment.
If find the argument that ‘we paid for it’ a bit childish.
Its not YOUR river, any more than it’s MINE. It belongs to everyone and everyone has contributed in numerous ways. Since the money seems important to you let’s talk about that. It’s £45 to enter the 3rivers race which helps pay for lots of things, but most work is done by volunteers. The swim, had a much smaller pool of volunteers so much was paid for directly. (Source - a chat with the organiser online.)
I doubt very much if much money was made, if any.
Perhaps the more grown up question is, if freeswimming is to become a regular thing, perhaps the BA could find a way of creating a contributing payment?
I imagine that this event was seen as a test so perhaps if it bugs you you should ask the BA.