I have done for my son 2 times. One time costs 6000$.
They try to hit it from all sides, they will put the kid on rotation diet, would do a compounded supplements on basis of kid's nutritional deficiencies, along with their OT exercises and academic stuff.
They do a pre and post testing.
After first round, the post test showed improvements but we didn't see anything, the center told us that all the changes were made in fixing the gaps he had in his sensory integration, so we must go for another another round to see the real changes.
We did another round, saw nothing. Though the post test showed improvement.