Surface water is best in terms of quality however is not hugely reliable in terms of allocation. buying temporarily is an option but price can vary a lot, can be expensive as it is now or cheap in a flood. Bore water is reliable (100% allocation each year) if quality is good, sub 1000ppm tds or sodium content is best. Salinity and soil structure impacts need to be considered if planning to use lots of bore water. Especially if salinity is higher. Pumping costs need to be accounted for. $50-60/ML is fairly typical. Both would need to be purchased if you have no entitlement of either. I’d say $1500/ML+ for surface water and $2000/ML+ for bore water.
pretty deep topic but hopefully this explains a little.