3up3dn -
In the 10th round last year the "slot" range was from
$65,000 to $5,000 for signing bonuses. I left out of these numbers the $600,000 paid to Matt Walker by Tampa Bay. You'll find a few of these exceptions in every round.
After the 10th round, signing bonuses are not reported but they will be in this $$ range or lower. A
few large $$ bonuses may be given to players who for various perceived signability reasons were not drafted until later rounds. Also, Teams who don't sign their higher picks may use these $'s to entice a "signability player" away from college with a larger bonus offers. But this is not the norm.
For most of the prospects drafted in the 10th round or lower, their bonus is the "chance to play pro ball".