I'm in a 12 team league where we can pick 2 players as keepers.
The cost is giving up a draft pick at least 1 round before wherever that player was drafted. For any keeper you carry into a second year, you have to give up a draft pick one round ahead of last years pick you give up, so every year a keeper costs a better pick than last year. This means players drafted in the 1st or kept from the previous season by sacrificing a 1st can't be a keeper for the next season.
Players have a minimum keeper value of a 10th round pick, so any FAs after the draft or players picked in rds11+ still cost a 10th.
On my roster I have Puka Nacua (would cost a 10th), Jordan Addison (6th), and Calvin Ridley (9th). Debating which two of these three I should keep,or if I should use one of my keeper selections to hang on to Anthony Richardson who looked great before his injury, or one of the Ravens RBs I have - Keaton Mitchell and Justice Hill. Mitchell looked like a sure thing to be the next starter before getting hurt.
I figure going deep on WR with my keepers lets me lean into a hero RB strat next season, so I think that's probably the way I'll go just want to make sure I'm not making a mistake.