I'm fine with it. If it costs more, then put more funding in. More teachers, more assistants, more incentives, training campaign. Modernize facilities, streamline expansion. If one school has less local funding than a school in a richer area, we should be able to compensate for that too. I'm sorry, but it all sounds like very common sense stuff and it's frustrating to see the country sit on its thumbs.
At the same time, work on other areas that will help decrease the number of special education kids in time (child hunger, child poverty, child abuse, substance abuse). Just dumping money in to schools alone probably isn't going to solo-fix the areas where the US is getting its butt kicked in education.
If a special ed kid is high functioning, adaptable enough, and can be effectively worked with, I don't see why mainstreaming them into regular classes would be a huge issue. some of the special ed kids probably wouldn't be much worse than some of the kids mainstream classes already have to deal with.