Wow! first time I've seen this. I have the newest Bandlab Cakewalk on an 8 core AMD with 16 gig. I was mastering a song with plugins from plugin-alliance, waves, etc... no prob..
I had even CPU distribution across all of the cores at about 15%. Then I loaded IK's Lurssen mastering console and my cpu usage on the first core shot through the roof and the sound playback started to stutter and pop. Really odd! So I used the new Plugin Alliance mastering box and finished the job, but I'm stumped as to what the IK's console's issue is. I really like it and I hope the wise people of out community can offer some advice. Thanks!

Have you tried using the VST2 version? 
 
I've had issues with VST3 plugins sometimes hogging the CPU (Antares EVO are the worst), and swapping to VST2 fixed it for me.

Don't forget that even though it's "just one plug-in," there's a lot going on under the hood, and plug-ins made specifically for mastering devour CPU cycles because, presumably, they'll be dealing only with stereo tracks. The plug-ins for multitrack recorders have to draw a lot less CPU power, or you wouldn't be able to use lots of instances.