Here's the theory behind drafting & roster building analytics. Draft picks represent savings. You could acquire a great player in the draft or acquire one in free agency. It's far cheaper to acquire one in the draft. This is the cap value of draft picks.
How much savings a draft pick yields depends on what position the pick is used on. A great RB might command $10M in free agency, while a great DE might command $35M.
The #4 overall pick in 2025 will make $7M. Using that pick on a RB saves you $3M, and using that pick on a DE saves you $28M.
This is why you don't use a rare #4 overall pick on a RB, no matter how good he is. It's just poor roster building.