Answer:
There is net transfer of energy and more over the balance between the number of charge particles occurs when there is some contact between any two surfaces or bodies. So, when an electrically neutral balloon is rubbed on a cloth and becomes positively charged it is just because of the number of charges that are transferred from a more charged body towards a body of having less charges on it. So, the masses of the positrons and the electrons are some how equal when compared.
Making, it more easy to understand that the two surfaces will have an equal number of positrons and electrons on both the bodies or object's surfaces.