Maybe it’s my inexperience. I’ve not had to define egress rules yet. I run 1 preemptible n1-standard-2 node and pay for ancillary services. It’s $35-40/month.
I have the equivalent of 2 n1-standard-4 nodes (a bit more performant, actually), rented as dedicated servers, for $30 a month. Including egress and bandwidth.
That’s why I disagreed with the "GKE isn’t more expensive".
$13 per month per egress rule, bandwidth costs a factor of 100 more expensive than dedicated hosters, and costs for hardware 10x of what dedicated hosters offer.
I’m not sure what your definition of "more expensive" is, but compared to renting dedicated hardware (e.g., from Hetzner), or colocating, GKE is significantly more expensive.
Of course, if you’re on the scale of Spotify, you can get much better deals – but from what I see on https://cloud.google.com/products/calculator/, it’s not cost-effective.