4.9k with 4 years of exp is already very good compare to those engineers in private sector. (of course financial/banking/accounting is out of the question).

most of my friends including me with 5 years of exp(inclusive 1-2 promotions) for MALE only getting 3.6k-4.2k range, all engineering private sector.

I had receiving info from my mum's friends, which they told her their son/daughter with 4-5 years exp in government job already getting 5k plus salary..

Got one working in manpower female already getting appox 6.5k with 7 years exp..
Other source like 5 years in DSTA getting 5k..

All is non-scholar