I think if anyone is expecting them to spend more then surely they ( the parents ) have a moral right to know what the therapy is and what the outcomes are expected to be
I've provided a link that provides all of the detail for a fairly trivial sum and offered to let you read the darn thing for free with a non binding request. I'm not going to paste the entire book here, nor rewrite it piecemeal. Many of the drugs are OTC medicines, the relevant supplements are commonly available. As to some moral right - can't see why there would be any. As to outcomes it will likely vary rather enormously based on
1) how much of the individuals autism is genetic - I expect that it will be insignificant in most cases but only twin studies data can give us a solid answer on how many cases can be expected to be primarily/exclusively environmental. There will almost certainly be genetically deterministic cases that anything but gene therapy would be unable to fix.
2) the particular pattern and extent of damage
3) how long the individual has had the autism