S Corp vs Sole Proprietorship - What's the Sweet Spot?

In a solo 401k, I get to do 22,500 for 2023, plus 25% of what I made. In an S corp or sole proprietorship, you're paying self employment tax on the whole 100 grand. So in an ideal scenario, holy crap, I could do 32,000 and still only pay FICA on 50%. That's where the SEP just doesn't make sense.