I dont think that ratio to special education says all that much. A lot of it is heavily disabled kids who do need expensive tools to even learn to walk and have kids-teacher ratio like 6:1 or even less. Mostly because they need a lot of support to just function - whether they are learning or not.

The gifted education is comparatively cheaper.

Plus, it is about kids that are bordering to being a danger to themselves or others. They need experts just to function. They are getting special education for the sake of other kids too. And failing their education means more money spend on prisons or social system once they grow.

People imagine special education being about slightly slower kids. But these are not costing all that much.