You can get a net positive utility gain from a net zero money gain with a continuous function, if it were say, logarithmic. A has 1X$ and B has 10X$, then an exchange occurs where 1X$ moves from B to A, now it's 2X$ and 9X$, but the change in happiness for A could be log(2/1)~=.30 while B log(9/10) ~=-.04
This is just one utility vs wealth model that would argue wealth transfers improve net utility in some contexts.
This is just one utility vs wealth model that would argue wealth transfers improve net utility in some contexts.