I'm not a bike shop but a neighbor asked me to fix their kids wally bike, I told them parts alone would probably cost as much as the bike did, they said it did not matter that they would reimburse me. When they saw that the parts did indeed cost $60 (they paid less then $100 for the bike) they refused to pay that much to fix it. So even without labor charges most wally bike owners would probably be better off getting a new bike then trying to fix the one they got.

Anyway I too will refuse to fix any wally bike as you can't replace hardly anything without it seeming absorbingly high for a $100 bike.