Last time I checked the GCP prices vs. hetzner servers there was a factor of 10 in monthly cost. So I cant say this is a general rule of thumb. It is true though that hetzner can provide superb performance per $. Potentially below what you can do (unless you buy racks of hardware).
They do have dell servers, too. But don't expect to run on one of these nodes unless the machine type has Dell / PowerEdge in their name. This means the management capabilities are minimal (but usually enough). A fully licensed management card can do way more.
Their renting pricing is ridiculously cheap though. Hardware failure is more common than on cloud providers (see cluster hardware), support has been helpful in the past.
Overall IMHO a good choice if you are price sensitive. But even then consider development vs. deployment vs. running (server) costs. Servers might make up less of the total cost of a service than you expect.
To be fair, companies that merely launch VMs on GCP constitute a small fraction. GCP truly excels when you leverage its object storage, BigQuery, managed postgres database (which starts at 7$/month), and serverless solutions for cloud-native applications. Our company operates around 500 services, with billing per second, and a significant number of them are scaled down to zero when not in use. If you need a GPU for a batch processing task involving 10,000 images, you can simply activate a VM equipped with a high-performance GPU for an hour, pay for that duration, and then shut it down. At Hetzner, you're required to pay for a whole month upfront, regardless of whether you need the GPU for just an hour each day.
Therefore, I'd argue that if you require continuous, raw computing power, Hetzner is indeed cost-effective. However, the cost-effectiveness elsewhere really hinges on your usage patterns.
Also keep in mind that hetzner is mostly a beowulf cluster. See e.g. this press picture from their newsroom page: https://cdn.hetzner.com/assets/Uploads/IMG-0546-91.jpg
They do have dell servers, too. But don't expect to run on one of these nodes unless the machine type has Dell / PowerEdge in their name. This means the management capabilities are minimal (but usually enough). A fully licensed management card can do way more.
Their renting pricing is ridiculously cheap though. Hardware failure is more common than on cloud providers (see cluster hardware), support has been helpful in the past. Overall IMHO a good choice if you are price sensitive. But even then consider development vs. deployment vs. running (server) costs. Servers might make up less of the total cost of a service than you expect.