"Wow jeez! 'Only' ten years! That's not so bad, I think I could live with that, now I think I'm gonna go pull a huge scam! But damn, if he would have got 20 or 25 years, then I'd have to reconsider my carefully thought out decision to commit fraud" -- Nobody, Ever.
To most people, just the act of losing everything you have, losing your ability to provide for your family or yourself. Losing your reputation, your career and future career opportunities, is enough to deter them. Whether a crime will give you 10 years or 20 years, most people consider that to be so long, that it's more or less all the same. It feels like an eternity, and it feels like your life is over. So if they are going to take a risk, or make a stupid decision, then they are going to do it regardless. Not because they accept the risk, but because nobody ever believes they are ever going to get caught. They consider that as "my life is over anyway". And usually, it is. That's not the point of prison. If you are ever going to let people out, why not focus on making sure they don't come back. Punishing people by throwing them in cages with worse people, absolutely does not work. (note: I am speaking mostly about non-violent crimes, which make up 72% of the federal system)