Anti-wholesale

On one fine Sunday, we ended up in Bekasi area looking for food to bring home. Mom spotted a hawker selling crispy sweet rolls (Semprong).

M: I have here Rp 5000, how much do I get for that money?
H: I'm sorry ma'am, I normally sell them in three packages for Rp 20000
M: No, I dont need three of them, how much is it for one package?
H: Alright, I give you one for Rp 6000, because normally it's Rp 20000 for three.

I wonder where he learnt his trade...