[rnbrady]

Sunk costs have no bearing on the logic that "if miners are spending more on electricity than the Bitcoins they mine are worth then they should immediately stop mining".

You're falling for the so-called "sunk cost fallacy".

http://en.wikipedia.org/wiki/Sunk_costs#Loss_aversion_and_th...

What does have a bearing is whether they intend to sell or hold those Bitcoins. If they believe the value go up before they sell, then they would continue to mine speculatively.