1/1 player means round 1 pick 1.
True, 20M college scouting means - usually, not always - that you can see a full 500 projected prospects. I've occasionally seen less, something like 450-ish.
However, those college prospects make better, more useful mid-level players. Your minor league teams will have older, higher rated players.
True, 20M high school scouting means you'll see only 200 to 300 projected prospects. That means lots of ??? players which means lots of lottery tickets. But only about your top 100 prospects will ever be any good at all. Kinda sucks to see your 120th rated prospect projecting to a 40 overall, and then you might end up drafting that kind of player in the 7th or 8th round.
These late-round gems show up in the college prospects too, not just HS. But as we're talking about them, remember that no one knows exactly how often or where they will show up.