I did a bit of research for you, since you posted that your son wants to play a grad year and be drafted. Mentioning that he was going to be a graduate student may should have been mentioned in the original post. Remember, he is now one year older, and it matters.
From 5th year grads (listed as "4YR5S" in the link below) being drafted, here are the rounds and the bonuses they received:
Round Pick Bonus
4 128 70K
5 156 20K
6 189 32.5K
7 202 37.5
7 203 25K
There are more. You can check them all here:
https://www.mlb.com/draft/tracker/2022/all
The link will also list what schools they were drafted from. I noted, just of the ones I listed, TWO of the 5 came from Louisiana Tech.
Just info I am passing on.