What if a high end speaker measures really badly?

Measurements are not important; it is how the equipment sounds to you that matters.

I’ll go out on a limb and assert that in the end, proper application of measurements always helps to achieve one’s hifi sound goals faster, more effectively and for less.

The trick is to be able to understand and apply the numbers properly and I think that is not easy but a worthwhile goal for any audiophile.

More good and reliable data informs better decision making. But the devil is always in the details. Practically though, each will end up finding their own way as best they can. Sometimes it’s the journey that matters more than reaching the final destination.

It’s all good. Cheers!

Efficiency is important to me as one of my amps (a class tube A SEP) has relatively low power...impedance is important, but the sound is really all that matters...and I'll never buy anything without auditioning unless it has a very fair return policy. 

@erik_squires - that's a very ragged frequency response graph. I don't think speakers have to measure perfectly to sound good - Wilson Audio speakers are not textbook. But there's a difference between small deviations and big ones.

@erik_squires I don’t think we can say much of anything about that graph, and the others presented here without knowing the level of smoothing applied to the raw data. As I am sure you know anyone who has played around with Room Equalization Wizard software knows that you can make a washboard look like a pancake with adequate smoothing applied to the chart. It’s frustrating because that critical piece of information is very seldom supplied with charts such as these when published.
this has been a nice thread so far, thanks to the OP and all the contributors. It has sparked some thoughts that perhaps I will share in another thread.