AMD opteron 16 core

So I am wondering, why is the AMD opteron 6376 about 700 bucks? I know it is a "server" processor but it benchmarks worse than AMD's FX-9590 by a significant margin, and also worse than the FX-9370 which costs just over 200 bucks. I am not at all well versed with servers, so maybe my question is noobish. I am sure that server tasks are probably much more scalable to multiple cores or cpus, but if the processor benchmarks slower accross the whole cpu (albeit the benchmark I am looking at might not necessarily be tuned towards server workloads but rather raw compute performance) then why would the opteron be 3x as expensive as a more powerful option?

Perhaps it isn't worth anyone's time in actually explaining this to me in a post but rather link me to something that explains it.

Thanks in advance.

 

Stability and efficiency. Opterons are designed for strenuous 24/7 usage and more stable, thus less likely to make errors. The FX can't really say that. Sure an FX may be able to 24 - 72 hours of strenuous usage (ie torture test), but it's doubtful it can do that error-free for one month or one week, yet alone 24/7/365. The opteron is also likely to give better performance per watt, which is very important if it's part of a large server. There are also other features that servers need that consumers don't, such as ECC memory, and, conversely, consumer hardware has features servers not only don't need, but could be detrimental to their designed use case, such as unlocked multipliers.

Here is a video explaining the differences, and CPU's are covered:

https://www.youtube.com/watch?v=ByI1PHMcPJQ