The thing is, the cost for the HVAC 24x7x365 support for a datacenter will be roughly the same for a given location... but it makes a difference if it is you paying the whole bill (=you're self-hosting in your own datacenter), you are splitting the bill with a bunch of other customers indirectly (=you're self-hosting in a colo DC), or if you're splitting the bill with a shitload of other customers (=you're using some service on one of the big public cloud providers).
The downside for saving the costs is that you're losing control with every step taken away: as soon as you go into a datacenter of any kind, you simply cannot call up a HVAC company and offer them 100k in hard cash if they're showing up in the next 60 minutes and fix the issue. With a colo DC you can usually go and show up there to see if the HVAC, UPS and other systems are appropriate to your needs, but with one of the big cloud providers you have to trust their word that they are doing stuff correctly.
The downside for saving the costs is that you're losing control with every step taken away: as soon as you go into a datacenter of any kind, you simply cannot call up a HVAC company and offer them 100k in hard cash if they're showing up in the next 60 minutes and fix the issue. With a colo DC you can usually go and show up there to see if the HVAC, UPS and other systems are appropriate to your needs, but with one of the big cloud providers you have to trust their word that they are doing stuff correctly.