Saw some of the posts above. I've been in the service for 5 years. Would like to say that yes, there are some who's starting pay really is $4k ish. It depends on 2 things:

1) What scheme are you on? Economists scheme for example pays well. Their starting pay for FCH is in from $4k ish.
2) Which Ministry/ Stat Board are you in? Uniform group have different starting salary tiers for different classes of Honours, and Stat Boards are more flexible. In fact, certain economic/ finance stat boards pay more than the Ministries.

For promotion and increment, again it depends on which agencies/ Ministries you're in. Certain Ministries are choke full of scholars; the probability of you having (faster) promotion is much harder than if you were to compare to your peers in agencies/ Ministries where there are lesser scholars. And it also depends on how much budget your agencies/ Ministries have ring-fenced for the increment/ bonus. This is also dependent on the Singapore economic outlook. If its bad, the % increment will also be lesser.

Would also like to highlight that there are scholars who are promoted twice in a roll, i.e. MX11 within 2 years. In fact I have personally seen one who was MX11 within 1 year; it was a combination of pure luck (the date the person entered service) and the person's academic accomplishments. And your bosses have to like you of course.

In summary, don't be a sour grape and complain when you see others (scholars or not) getting ahead of you so fast and earning more. If that is the case, then you are better off in the private sector, where you have a more "equal" opportunity to prove your worth. Mind though, I reckon it'll be the same regardless private or public.