baby sitting advice?

Annah • PROUD MOTHER OF TWO !! Married to the loml!!! 22 years old!!!
Okay so I asked my sons grandmother on his fathers side if she could watch him for a couple hours and her response is "How much are you gonna pay me? Lol" 
I'm not paying his flesh and blood to watch him for two hours that's ridiculous .... am I wrong to feel like I shouldn't have to pay her to watch her own grandson she should already want to...