> Does it make sense to go cloud (even spot) when I would aim at high utilization?

Hybrid cloud ?

"combines and unifies public cloud, private cloud and on-premises infrastructure to create a single, flexible, cost-optimal IT infrastructure."

Hetzner has a dedicated cheap server: ( monthly pricing )

https://www.hetzner.com/de/dedicated-rootserver/matrix-ax

- AMD Ryzen™ 5 3600 ( € 37.30 + VAT) / month

- AMD Ryzen™ 7 7700 ( € 59.00 + VAT ) / month + setup

- AMD Ryzen™ 9 5950X ( € 103.30 + VAT ) / month

- AMD EPYC™ 7502P ( € 119.80 + VAT ) / month + setup