It almost made my heart break

Yesterday as we were driving home from school, I broke the news to the kids that their favorite person in the world, the babysitter, would no longer be a weekly angel appearing on our doorstep. After reassuring C that it wasn't because she didn't like him anymore, but because we needed to save some money to help pay for the new house, he grew silent for a minute. Then-

C: "Mommy? Next time I go to the bank with my piggy I will save the money and give it to you and daddy to pay for the house instead of buying a Thomas train."

Mommy (trying hard not to cry): "Oh, sweetie, you don't have to do that. Mommy and Daddy can afford the house without your Thomas money. We just need to be more thoughtful about how we spend for a while."

C: "No, really, I want to help pay for the house. But there isn't much money in my piggy right now because Daddy and I just went to the bank. (pause, then rather sadly) Should we return Thomas? I've already played with him though..."

Mommy: "Oh, C. No. Thomas is all yours. And really, your piggy money is yours. We're fine without it."

C: "Well, OK. But since we bought the new house so I could have a bigger room that doesn't bounce, I feel like I should help pay for it..."

I feel like I've done something right and wrong all at the same time.