Re: Cloud costs
"Is it really though?"
Yes. Some of those problems become easier. Monitoring your kit on the cloud, for example, is a bloody doddle because it's all built in. Likewise backup becomes somewhat more straightforward because of object storage (recovery is another matter). Some problems become a lot more complex. Key management on public cloud infrastructure is a nightmare, for example, and it's not unusual these days to find complex two- or three-layer deep encryption to tick all the compliance boxes.
There are two big increases in cost. The first is the per-server marginal cost. If you're paying on-demand pricing you're looking at something like $3500 per year for a single, relatively small instance (e.g. c4.2xl@8vcore/14GB). This may look small, but it's huge.
At typical utilisation rates you could happily shove 10-15 or more of these instances on an HPE HC380 on-prem, and one of those will typically set you back about £10k after discounting. The per-instance-per-year price is an order of magnitude greater than the capital cost of the physical kit. If you're at a certain scale (and the Home Office is) your amortised ops costs do not come close to putting a dent in that cost differential.
So you don't do on-demand pricing. Which brings us to cost number 2. All your applications now need to be made fully capable of exploiting cheap capacity via spot pricing and lessening your base costs with reserved instances. That's potentially a huge application investment - most enterprise software was not designed to elastically scale.
There's a potential third hidden cost in the data ingest/egress charges but thankfully most people are savvy to those now and don't get caught out.
Cloud is a lot of things, but only very rarely is it cheap.
The one model that is radically cheaper is SaaS (e.g. Workday vs SAP on-prem), but you're buying into quite a lot of lock in to get those benefits.