EKS is priced at $876 / yr / cluster at current rates.

Negligible for me personally, it's much less than either our EC2 or RDS costs.

Yeah, using EKS isn't the same thing as "administering k8s", unless I misread you above. Actual administration is already done for you, it's batteries included, turn-key, and integrated with everything AWS.

A job ago we had our own k8s cluster in our own DC, and it required a couple of teams to keep running and reasonably integrated with everything else in the rest of the company. It was probably cheaper overall than cloud given the compute capacity we had, but also probably not by much given the amount of people dedicated to it.

Even my 3-node k3s at home requires more attention than what you described.