Meaning of そんだけ in this context


丸尾 is assertively ensuring that his teacher remembers his name. The teacher
replies:

> そんだけ売りこめば忘れたくても忘れないよ。  
>  If you sell yourself (arrogantly?) I won't forget even if I wanted to.

Im guessing that そんだけ derives from そんだい. If so what is the grammar? How would
it differ from そんだいに?

**Edit:** just realised that this guess is probably nonsense because there
would be no reason to remove the い. Nonetheless, I still don't understand what
そんだけ means in this context.




それだけ(soredake)：So much  
↓  
Omission of the pronunciation  
↓  
そんだけ(sondake)




それだけ(soredake)：So much  
↓  
Omission of the pronunciation  
↓  
そんだけ(sondake)

