http://m.mlb.com/news/article/...g-and-bonus-tracker/
The link above will list the slot value and the actual bonus, but only for the first 10 rounds. After round 10, teams are penalized (fined) for amounts over $125,000 (I think this is the new amount this year), but you will see a lot of college seniors go for $1000 or $2000, since they don't have the leverage the college juniors do.
So, $10k, 20K, and less is very common, especially in the later rounds, for college seniors. You will also see a drastic dip in many bonuses in rounds 8-10 (where teams will also pick seniors), so they stay within their slot amounts (their budget).