my two cents (from personal experience): Getting money when you are from low SES is not that stimulating, because the money is inevitably spent on mundane purchases: i.e. buying a new pair of school shoes or school supplies, or beef instead of chicken for a meal that week, or fixing your car.

If that money would be able to be spent on anything that the child desired, then I am sure that even a lower-SES would be more excited.

I fundamentally believe that the higher-SES you are, the more agency you have (especially financial), where lower-SES are in constant survival mode. It is hard to get excited by small sums of money when you know that it will just be immediately spent on boring things.