"But autistic people are likely to be in care for life!"
Let's have another gallop past some real info.
https://files.digital.nhs.uk/publicationimport/pub16xxx/pub16133/comm-care-stat-act-eng-2013-14-fin-rep.pdf is community care info for England. This one, 2013-14, as an example.

There's about 55 million people in England./

About 3 out of every 100 are autistic. How do we know this? This whacking great national study from Northern Ireland, for example. https://www.health-ni.gov.uk/sites/default/files/publications/health/asd-children-ni-2019.pdf
So, number of autistic people in England, about 1.65 million.

Here's a fairly recent NHS document about people in England are in residential care. Here's a chart from it. They bung all autistic people in with 'learning disability' for reasons unknown. Just under 50,000 people age 18-64 in residential care, in total.
https://files.digital.nhs.uk/publicationimport/pub16xxx/pub16133/comm-care-stat-act-eng-2013-14-fin-rep.pdf

So, about 30,000 people with a learning disability are in residential care, age 18-64, in England, in 2014, if that chart is right.
Let's assume, wildly, that the autistic people are about the same number, spread between all categories. That would be less than 2 in 100.

And no matter which way I do these numbers, from various documents, I come up with the same set of answers.
The number of autistic people in residential care is likely to be about 2 in 100, not 100/100.
Yes, some others will need support, but this post is about residential care

Someone will say 'but what about those over 64, Ann?' Our average lifespan isn't 64, alas. So yes, there'll be some.
"What about those under 18?" Not many in residential care, to be honest, just for autism.
Also, almost none of the autistic people are *only* autistic/

What we see is an endless mystery - that if someone is deemed autistic, 100% of the care costs are dumped into the autism box. Supposing they also have a learning disability, EDS, a heart condition, a physical disability? Supposing *those* are the reason they are in care?/

I would very much like to see accuracy.

Every autistic person is a person of full worth, as is everyone else.

But we need good data, not wild scaremongering.