[acdha]

> If you have a little spare capacity, developers can still get hardware/software on a whim, at just a (comparatively) small one-time expense. Spare capacity is much cheaper than people make it out to be.

Those people are speaking from greater experience - there are many things which seem easy but aren’t once you’re over a certain scale, and at large organizations you often have things like conflicting policies or coordinated demand (e.g. your slack capacity disappears when every project is trying to hit the same budget deadline or a change moratorium ends, a pipe breaks in building A and you need to shift a ton of previously-stable systems for 6 months, etc.).

You can do that kind of capacity planning well but it’s harder than it looks and often politically challenging because the benefits aren’t obvious. Cutting corners looks like saving money right up until it doesn’t. If you aren’t buying servers by the hundred or storage by the petabyte, you are unlikely to be competitive with a cloud service without sacrificing multiple of performance, reliability, timeliness, and security.

[kqr]

I think you and I are saying basically the same thing, only putting emphasis on different aspects due to our various historic experiences.

Look at your demand pattern (variable or stable, predictable or unpredictable) and what cost structures your finances can support (variable or fixed, up-front or as-you-go), pick a solution based on that, not what's cool.

[acdha]

Also adding your barriers to entry: staff, facilities, process, etc. It doesn’t help you saving on servers over a cloud provider if your procurement process means you have people sitting idle for 6 months.