Interesting question. Perhaps you should look at the cost of spacecraft engineering for an example. You can't replace the hard drive on a probe billions of miles from earth!
I think what GP is proposing is significantly different than space craft: in space, you have limited space for redundancy, so you overbuild to avoid failure of key parts.
I think GP is proposing you start with, say, 11000 servers when you have a planned capacity of 10000, and just cycle off bad ones for spares (or just diminished capacity) until you redo the whole system.
I believe that's how Microsoft operates their server farms, but I could be mistaken.
Space is craaazy expensive for a lot more reasons though (ionization and lack of mission-redundancy are the big ones. Every launch is expensive, so every mission/satellite must have a bazillion nines).
