Latest Quantum Computer available commercially - D-Wave Quantum Computer
Costs: $15,000 (That too un-configured for Bitcoin Mining, coding will cost additional man's salary)

Quantum Computer Operation: Well you will probably need a room or at least superconductors which would be cooling down your 2000Qubic chip down to the -273 degree celsium.

If you have money then it's fine, buying computer worth $15 million wont be big deal for you. The question is would you be able to maintain the temperature below zero degrees all the time? Imagine the power consumption required to do that one.

Forget about break even point, you wont be able to recover the yearly power consumption out of the bitcoin mining.

If you start to inject the market with heavy supplies of bitcoin, assuming you are mining 1000x others, then ideally the supply will easily fill up the demand and might reduce in the pricing.

For example, Supercomputer in China, named Tianhe-2 use 18 megawatts of electricity.

In conclusion even if we use it, it wont be beneficial at all.