I assume, if I suddenly had reason to scale, I could call my colo and get another slot from them pretty darn quick. They're local and quite responsive, though I do get a feeling their "public shared rack" offering was created to deal with me. I was the first server in it...

Not everything "has to scale." My stuff isn't built to, and I see no reason to do so.

It's my personal server. I run some stuff for my convenience, a quiet backwaters community forum, a Matrix chat server, etc. If any of that really starts to ramp up, I can always split it out into its own VM. If it exceeds what my current server can handle (exceedingly unlikely), I'll go rack up another box for it. And if I get a super sudden spike in traffic, something is probably quite weird. The only thing likely to see that is my personal blog site, which I already have cached in Cloudflare with a typical ~60% cache hit rate, going up north of 90% if there's a spike in traffic, because, being a static site, I've told CF to cache "literally everything there."

I probably could move most of my stuff to "the cloud" in an evening's sysadmin, but... why? I already went through the process of moving it off the cloud to save myself an awful lot of money.

Here's Let's Encrypt doing just that: https://letsencrypt.org/2021/01/21/next-gen-database-servers...