Yeah I agree. Those numbers may be a bit high to aim for at a C- prestige team. Heck, I still had trouble finding players with all the cores mduncan mentioned even with an A+ prestige.
When I first started at Macalester in Wooden (C prestige), I was a brand new to this game. I was advised by some veteran coaches to shoot for the following minimums:
Guards (both PG and SG)- 65-70 speed, 40 Def
PG- 60PASS/60BH
SG- 70+ PER
Post players- 40-45 ATH, 40 DEF, 70 REB, 40 Def
at least one post player with 70+ LP would be ideal, and one with 80+ REB
SF- at least 40 DEF, but you will probably fill this spot with either a SG type (60+ spd, 40-50 ath) or a PF type (40+ath/40+spd/40+reb). Some LP and PER would also be ideal.
Keep in mind the above numbers are not starting ratings. They are minimum targets for a player's junior and senior years. If you can exceed those minimums that obviously would be great. Above all else though...ATH/SPD/DEF should be your priority categories. Be willing to make sacrifices in other categories for a little extra of each.