first of all, mass contributes more to escape velocity than density. V_e=k*(m^(1/3)d^(1/6)). (scaling the mass is quadratic compared to scaling the the density)

first of all, mass contributes more to escape velocity than density. V_e=k*(m^(1/3)d^(1/6)). (scaling the mass is quadratic compared to scaling the the density). Second, the density of rocky planets is bounded from below pretty close to the density of earth.