1) Once you develop a culture of PaaS the reality is, if you check the history of most startups, you'll continue along this way, and the money you'll burn will be massive. I suspect that if you build a sysop culture earlier, later you'll be able to just hire a full time sysop instead of spending a lot more.
2) If you don't understand very well your platform from the point of view of operations, likely you'll build a non scalable system (scalable not just from the point of view, let's distribute the load among N nodes, but about the constant times / CPU / energy it takes to serve a request). You'll end spending all the time again porting your app to another framework / language. This happens all the times.
3) The first months of a startup are usually not so critical from the point of view of operations, it is unlikely you'll spend a lot of time managing servers, unless...
Unless you selected a platform that is too complex to start with. I think that many of the PaaS companies I see today are here mainly for two reasons: Rails & Java frameworks.
So first of all, select your platform wisely.