He received a "$20k/year engineering scholarship, which is almost effectively a half ride (around 45k/year for out of state), while Duke gave [him] nothing." So, it's about a $100k difference over 4 yrs. See
Duke vs. UMich
I was in a similar situation. Accepted to Michigan in BME with a $10k/yr scholarship OOS and chose to go to Duke. Admittedly, Duke's financial aid gave me a lot more than nothing and Duke ended up costing less than Michigan so my choice was a bit easier!

Good luck!