I would argue that ROI is extremely important in education. It's just that the "return" on our investment is not purely financial. Producing students who will be competent to effectively participate in and wisely run the society of tomorrow is a large part of the return that we seek. So, to that extent it may be that high special needs costs are worth it if they demonstrably help students become self-sufficient instead of dependent wards of the state. I can't say for sure that they are worth it, I'm saying that the mere fact that they're expensive doesn't mean they aren't cost-effective in the greater sense.