I think they're asking about how to go about making it though, not having it made. That's a different thing entirely. You can make a suit that looks very accurate out of craft foam, if budget calls, or you can make it with plastic, or fiberglass, or resin, or even metal. It depends upon what the person wants, and what they can afford.
Just because it cost someone $3500 to have Halo armor made for them, doesn't mean it would cost anywhere NEAR that much to make it yourself...remember, you don't have to pay for your own labor, which I wouldn't doubt was a large portion of that price tag.