That is exactly my point though.I think DRK3 is correct. This is a 2 point buff. Assume the opponent plays Nauzica Sergent or SwordMaster or anything, which is a 4 strength card. You play Professor. You put 6 point body on board, remove 4 point body and gain 4 coins. That is a 14 point play (and with coins being traded more effectively with other cards, this could be even more). The damage you do on a bounty card by using coins is worth 2 points. That is the reason Slander is worth 6 points even though you gain only 3 coins. Assume you have Executioner on board. Opponent has a 3 point body. Now you use Slander and kill that unit. You have killed a 3 point body and got 3 coins back.
Any damage done to a bounty unit is worth 2 points. Since you are going to get the coin back. I know that if the unit is boosted it is not the case, but for the sake of this Professor's argument if we see her previous reach and now, previously he would play for 6+3+3 and now he plays for 6+4+4 which is +2 points and with a very reliable removal potential.
It is a 2 point buff if you kill that 4 point unit with Professor alone.
If you are using Executioner + Professor you could have gotten the bounty for a 4 point unit before the buff by extending the damage, which costed you 1 additional coin, which is the 1 damage buff.
In the previous case you spend 1 coin to kill a 4pt unit and get 4 coins, yielding a 6 (body) + 3 (damage) + 4 (for the bounty) = 13 pt card.
Now Professor allows you to deal 4 damage and you get a 6 + 4 + 4 = 14 pt card.
Let us say you have 3 coins and an Executioner and you want to kill an 8pt unit.
Previously: Spend 5 coins + Professor => Professor is worth: 6 + (8-5) + 8 = 17 pts.
Now: Spend 4 coins + Professor => Professor is worth: 6 + (8-4) + 8 = 18 pts.
My point is that Professor is only worth 2 points more than before if you do not combine him with other cards, if you do it is only a 1 point buff.
Edit: I guess one can also summarize this by saying the bounty itself is not worth more than before if you can trigger it in both cases (which is more consistency in collecting the bounty on larger units and being able to immediately kill larger units).
I am also a bit confused by your Slander example, why is Slander only 6 points ?
Slander gives you 3 coins and then scales with whatever can kill the unit with Bounty, if you bounty a larger unit you get significantly more coins than 3.