Kids and Going to the Store

We went to the grocery store today, and LM wanted a Curious George book that cost $3.

No big deal, right?; we could afford it, and I would much rather buy him a book than some dumb plastic toy. 

I tried something new today though because I would like him to learn that there are consequences associated with purchasing items.  

I told him that he could have the book but that he would have to "pay" me with one of his toys from home.  He said OK.  When he got home, I told him to pick out a toy in exchange for the book.  At first, he offered up his tricycle, but I didn't think the "worth" of the book and bike were equal, so I told him to pick another toy.  He picked one of his trucks--not an absolute favorite one, but not a clunker either.  Perfect.   

I took the truck and put it up in the closet.  He didn't even fuss about it. 

Don't know if this is the right path or not.  Maybe I have been reading too many financial books lately...

I want him to have and to see different money patterns than that with which I grew up, and I want him to understand that he has the power to make choices about his money and life.