I've been using AWS for the past 12 months. The beauty of it is that I have more time using the DB rather than managing it.
I'd be fascinated to know how it all works so well for the various RDS's and if you talk to an AWS engineer they will tell you but I don't have to know.
In terms of "quickly" there are price points for the size of the instances. The point is that the servers are treated on a "cattle not pets" principle. You get what it says on the tin. On- premise I might try all sorts of tricks to eak every last bit out of the CPU, memory and disk but I would end up with a huge job come hardware upgrade time to implement what has become a bespoke server.
Cloud DB Servers mean you have to rely on architecting your solution correctly and designing your schema properly. Failing to do so results in a big bill every month.
If you are smart you will use this as a lever to get things fixed.
In the UK the cost of the equipment can be capitalised over a number of years to spread the cost. This can be used to hide various evils. In the cloud it is operating expenditure and you pay straight away.
On premise there is the sheer Joy of practising craftsmanship but the misery of all but a few being oblivious to it