I think one of the sad things about Singapore healthcare is that public and private services are almost mutually exclusive. I.e one can't work for a public and a private institution (at least not officially anyway), hence there will always be pay comparision. This is among all specialities (not just fm).

I guess at the end of the day, with current inflation rate, we are all mercenaries lah (who doesn't want more money lol).
Fp who earns 8-9k will compare with private chain gps (13-14k)
Private chain gps will compare with those opening their own clinic (? 30-40k depending on your business acumen)
Public specialist will also compare with private specialist...

End of the day, we all want money over patient care..