Exactly, the cost of turning on additional servers is measured in ~US$100's/mth vs an engineer's time ~US$10k-25k/mth.

If you can make the problem go away by spending more in servers always do it.

For startups, the life and death is product market fit and you only get there by iterating on the business as many times as possible, not making something more efficient.

Put engineers on business iterations.

Using more machines also introduce complexity.

Even before using more servers, one should consider using (one) bigger server (and another as backup).

Massive servers are laughably cheap these days. E.g. 16 cores, 128GB RAM is €112 from Hetzner.

Damn, wish those dedicated servers were available in Hetzner's US data center. As far as I'm aware, the closest thing to a competitor in the US is OVH, and the server you get for that price is about a quarter of the capacity. That's plenty for my little company, but still...

Same here -- I'm eagerly awaiting them having a dedicated server offering

In the meantime have you looked at leaseweb?

https://www.leaseweb.com/dedicated-servers#US

I'm planning on running nimbus web services[0] there and there are a few other smaller providers I have earmarked depending on how brave you are:

https://www.defendhosting.com/usa-unmanaged-servers/

https://cc.delimiter.com/cart/dedicated-servers/

https://greenserver.io

[0]: https://nimbusws.com

In our case, we're running on top of a PaaS (think Heroku). Vertical vs Horizontal scaling is essentially the same complexity for the scale we're currently at.