The BIG SHOT atop the Stratosphere Tower launches me up the spire at 4.5 G's. (Maximum kinetic energy, minimum potential) At the top of that trajectory I float 1049 feet above the Las Vegas Strip! (Minimum kinetic energy, maximum potential energy)
How much energy is in an object? We always measure gravitational potential in relation to some other point. An object's potential is measured from Earth's centre, but that is only a tiny portion of the total. The object has more potential from the Sun. We don't feel the Sun's much greater pull because we share Earth's 19 km/sec orbital velocity. (Even many physicists don't know that the Sun exerts a greater pull)
There is still more potential from the Milky Way galaxy, to say nothing of all the other objects in the Universe. To find the total potential of an object, we would have to sum all those up! (Remember that R = ct and GM=tc^3)
Does anyone want to argue with this E = -mc^2 business?
To avoid confusion, we'll rename Eu as U = -mc^2 the Newton energy, and call E = +mc^2 the Einstein energy.
E + U = 0.
So the total energy of any object is just 0! This applies to any mass, no matter how large or small. Though there is no room to prove everything, this result also applies when you add kinetic energy, and even for massless particles like photons. (Anyone care to guess what the energy of a vacuum is?)
The total energy of the entire Universe is 0! It's the ultimate free lunch, which is how the Universe managed to expand from a tiny point to the complexity we observe today.