Raising a Thrifty child?

Raising a Thrifty child?

We went to a picnic last Saturday.

DS was playing with the other kids when the ice cream man rolled by. Two of his friends ran and got some ice cream. I was sitting right next to their play area so I discreetly whispered in DS's ear, "Let's not buy ice cream here anymore. We've got some at home if you want some, ok?" He nodded and continued to play with his other friends. When the 2 kids who got ice cream came back, they shouted excitedly, "If you want ice cream, go now or else you won't get any."

To which DS replied,
"My mommy said we can't buy ice cream here because it's too mahal(expensive). And we don't buy mahal."

This made me laugh so hard.
What have I done?!
Have I ruined my son's carefree childhood days by making him conscious of the cost of living too soon? Or am I raising my son to be a thrifty child, aware of our family's simple lifestyle?

DS, by the way is 4 years old.