Thanks for the reply Artem!
Poked around in the CLI, it looked like my account was set for 30 CPU. Used the command you posted to increase it to 100 and restarted the game client; now it's showing 100 in the client. So sounds like it was set to 30 when I first started the server, and stayed there.
All good here. Thanks!
I'm running a private server on my local machine (1 user only, i'm not a fan of competition), and recently hit GCL 2.
The UI is reporting CPU max usage is still 30. Game.cpu reports the limit for my GCL, though some searching says that always happens (link). It reports my bucket is at 10000 and tickLimit is at 500, which neither prove nor disprove anything...
The server is running as a normal process using a Steam API key so that I can play other Steam games while it runs in the background.
Just in case there was something wonky with subscription weirdness, I checked on the Steam store page too, and it says "Buy CPU Subscription Plan Raise your CPU limit to the point depending on your game level. Affects the official MMO world only."
So hopefully this is just a bug or oversight 
(Fun tidbit - while writing this up, I kept having to go back and fix "GPL" to "GCL". old habits...)