The problem is a lot of server admins claim it costs $1000-2000+ a month to run a unmodded minecraft server (with ~100 players). And a lot of players simply accept that as true.
Mojang ain't helpin' here. If you run a server and have lots of players on, or whatever, you'll see all but one of your server's cores idling by. 'tis sad.
..so lots of things will be cpu-frequency-bound. Memory consumption is another thing, but if you have lots of memory and SSD, your server will be able to do things. Still though, I believe the way everything is written, it's a very uneconomic use of hardware resources.
Instead of focusing on core code and overall quality and performance improvements, Mojang just keeps shitting out new game features. I see their rationale (short term $, etc.), but when they then go about talking about how they don't like large expensive server operators taking money, it kind of puts me into an angry mood.
We could have saved some money by using a cheaper European provider (iirc OVH had a similar spec'd server for £200), but we were all based in the UK so the low latency was a major benefit. The UK server provider market really needs some disruption.