One thing that people fail to realise, and perhaps why trades are not the best idea in Australian sports, is the cost.
I would imagine that each club has to bear the cost of relocating the player + family, packing up and moving, find temporary housing, accommodation, car rentals, schooling for kids, etc etc. For a company to relocate an employee from one city to another it can easily pass $50k +. Imagine clubs like North Melbourne or Port Adelaide having to find extra funds every year to pay for relocations on top of their 'free agents' relocations.
Certainly the NBL would struggle, with clubs running very tight budgets as it is. Even 3 player trades per year would probably add 200k to a club's running cost.
Perhaps not a a problem for the Collingwoods or South Dragons though.