I'll try to respond to everyone, but I'm on mobile:
1. I get where it sucks if this guy is telling the truth. And yes, paying support for a child who is not yours also might suck. But I believe he had multiple chances to say this to a court, and for whatever reason chose not to. His truth of not getting lawful notice is, in my experience, exceedingly rare and should be doubted heavily.
Its possible I'm being too harsh on the guy, but I doubt it. If a guy dodges notice or willfully ignores it, that's on him. He had his chance to get justice, and chose not to.
And like I mentioned, there is also, if he's right, a good chance of this all being undone, so I don't need to get up in arms over the system's "injustice". There are procedures in place to redress this stuff.
2. The FL paternity test - this thread is literally about one party, be it man or woman, lying to a court. Why should this Florida court believe either person? Isn't a neutral, scientific test what people want?
3. Misunderstanding of what child support is. It's not what it costs to raise a child. It's meant to somewhat approximate the level of finances the child would enjoy had both parents been together. So at each parent's household the child gets similar levels of treatment, so to speak.