Every roster is going to cost a minimum of $10m to be competitive in the power conferences no matter how you build it. If you build it through the portal, the going rate for a medium-top level transfer is $1.5m+.
If you build through high school and develop guys on the cheap, once they get good you have to pay them as well. Sure, you might get a discount, but anyone that averages 15+ points and shoots well from three knows they are going to get $1m+ if they put their name in the portal.
So you're going to need $2m each for your top 2-3 guys. Maybe $500k-$1m for the other two starters. $350k for your 6th-8th guys. $150k+ for the rest of your roster. $6m (top 3 starters) + $3m (5th-8th) + $1m (rest of the roster).
Top top level teams like Duke going to start getting in the teens for their roster spend.