"You have to get value for the water and any water over a dollar...

"You have to get value for the water and any water over a dollar a cubic metre starts to be a liability at viable scale."

You obviously aren't near Arizona, where desalination of seawater from the Sea of Cortez is under active consideration because of groundwater depletion and lower flows from the Colorado River. And people aren't even talking about sale of the byproducts. One reason our groundwater is being depleted is that the Saudis are using farmland to grow silage that is exported for their dairy cows. Since that source is threatened by legislation, desalination is an option for them also.

Low-concentration Duperow brine, with all its contaminants that need to be removed, is still a more likely source for DLE. Low cost of entry, low processing costs -- all of those will lead to a supply glut. DLE is more likely to kill the lithium market than to save it.