You can't equate Gralats to real money in this scenario because it's not intended to be a paid position.
It's always been a volunteer position, receiving Gralats for it is more like a thank-you bonus than a method of payment for their service.
It's not child labor because they know they are not going to be paid in real money before they start working and they are free to leave whenever they want and aren't forced to work a certain amount of hours, although I believe there is a minimum they have to do but it's pretty low and makes sense because if they are barely doing anything there's no point in having them along. Obviously there is exceptions to this but generally it prevents people from becoming an admin and then not doing anything.
Given there's about 730 hours in a month, 50 hours isn't really that much.