All for an Extra Piece of Betel Nut

Just for few days, I have decided to chew only the betel nuts (without the pan leaves so as to avoid reddening my mouth) This episode Just happened at a Panshop:

Me : How many doma khamtos for Nu. 20 ?

Arrogant Shopkeeper Ama : 8 khamtos

Me : I just want betel nut only .. no pan leaves. How many pieces will u give for Nu.20?
Arrogant Shopkeeper Ama : 8 pieces only.. with or without pan leaves

Me : Please, give me atleast 9 pieces.. afterall I'm not taking the pan leaves

Arrogant Shopkeeper Ama : NO.. dont waste my time. Take it or leave it.

Me : Ok, Give me doma Khamtos for Nu. 20. (I pay Nu. 20) 

(Arrogant Shopkeeper Ama gives me just the 8 pieces of betel nuts )

Me : Give me the pan leaves also

Arrogant Shopkeeper Ama : Why? You said you just chew only nuts.

Me : Give me my money's worth of Doma Khamtos. It's not ur business whether I chew just the betel nuts or with pan leaves.

(Arrogant Shopkeeper Ama gives me 8 doma khamtos. Right there, in front of her, I promptly pocket the betel nuts and then tear up the pan leaves into pieces and fling it into the dustbin.)

Arrogant Shopkeeper Ama : Hey, why did u do that?

Me : My wish. You could have saved that eight pieces of pan leaves if you had just given me one piece of betel nut extra. I'm a commerce student.. I don't let others derive the maximum marginal utility out of my money!!!