How do pressured containers within pressured containers behave? If a container could hold 60 PSI of pressure and was placed into a larger container with the same strength, could you fill the large container to 50 psi and the smaller one to 100 psi, creating only 50 psi changes?
If so, could you do this infinitly, having compressors in each tank feeding to a smaller one within, allowing you to build a huge pressure?
 A: As you suggest, you could use a large number of nested containers to gradually increase the pressure of the innermost container to very large values.  Generally it's only the pressure difference that matters.  These could even be weak containers, like a balloon within a balloon within a balloon within...
But this can't go without limit.  Once the absolute pressures acting on the container become significant to the structure of the material of the container, this approach no longer works.  This generally occurs only when the pressures are high enough to change the lattice structure and/or other physical properties of the container material, and this is generally only at very high pressures: think of things like coal becoming diamond, nuclear fusion, etc.  (This is probably fairly obvious, but just as an example: at a 1 psi differential for each container, everything inside your one-trillionth container will be at the same pressure as at the core of the sun, and just as a balloon wouldn't survive inside the core of the sun, it wouldn't survive in the one-trillionth inner container either.)
