Probably more than you'd guess. Nostalgia is a powerful drug.
https://www.nblstore.com.au/collect...les-22-23-nbl-throwback-jersey-corey-williams
https://www.nblstore.com.au/collections/throwback
There're leagues where defunct team's merch is amongst the highest sellers when it's produced. The Houston Oilers, Seattle Supersonics, Montreal Expos, Hartford Whalers, Quebec Nordiques, and Vancouver Grizzlies, would all be making a tidy sum for their respective teams and leagues annually.
It's actually an area where the NRL has really f**ked up. It's a travesty that they allowed so much of that old IP to be lost to the game.
You need to lay off the crackpipe if you think Kestelman and the NBL would be open to selling at all, let alone for as little as a $100k. They don't need the money and there're easier ways of making it even if they did, like selling more Townsville Crocodiles merch and streaming more of their old games for example lol.
Going to court would be expensive and the NRL would almost certainly lose. It wouldn't be worth the risk, especially not when there're so many workable unique branding opportunities for a PNG side.