I think lingual braces will cost more than invisalign. They aren't
cheap & if you have both upper & lower jaws done it's alot more money. Here in the uk I think for both jaws you'd be looking at £7,000-£8,000 or around that mark. I don't think invisalign is that much for both jaws. It depends on the case though but I know linguals are pricey. You can half the price near enough if you have lingual upper & ceramic or metal lower. That's what I did but my bottoms were too twisted & rotated inwards to get the brackets on them so it made my decision much easier.
Sorry I thought you meant invisalign would cost too much but don't think you meant that whoops lol