I'm assuming he means money as in time, to install, configure, optimize, and monitor those distributed systems.
Granted, I am not monitoring Kafka, but I do other processes.
The other nice thing is that now that I have ZK, other software that need it can just reuse the same process.
I think using the maintenance cost as a reason to write your own tool, is a short-sighted decision.
That just leaves the "simple work" of administering and tuning which, as you pointed out, is competence that's steadily growing in the industry.
Simple code with "obviously no bugs" vs complex code with "no obvious bugs".
This is one of our biggest headaches, and it's not even that a Kafka server itself is so configurable. We have hundreds of teams writing client applications, and jumping on bridges because Kafka clients have poor configurations is getting old. Too many knobs to twiddle, but I guess that's what happens if you're expecting to be able to tweak for high performance.