One of the reasons why Political Office holders are prepared to be involved despite the low pay is opportunities and avenues that are opened up after they leave office. The Western style democracies have evolved not necessarily with altruism in mind. The notion that you can find something lucrative down the road has always been a magnet for people to participate in politics. The trick is have an appropriate controls in place and a transparent process and culture in place. The PAP unfortunately was never about transparency nor interested in being accountable to the populace. There are no controls except that the PAP keeps mentioning CPIB and the mantra of incorruptibility as propaganda. In Oz, when Kevin Rudd became PM, his wife sold her business and put her assets in blind trust. That is a classic control. PAP has none of that.
Remember the clown who ran the SGX. He had a stake in a company which he founded that was directly competing with SGX his employer. It only surfaced when it appeared in the foreign press. He eventually put it in blind trust and left only to join Temasek. What kind of signals does it send to anyone who has a shade of morality.
The primary reason why the huge salaries structure was proposed and implemented was to attract quality people into PAP. Something that is not faced by other western democracies. People do not want to be associated with the PAP and if they have to , they want to be appropriately compensated to cover the shame. That's is also why the President's salary was raised 3 times to an astronomical size after the last elections before no one of professional standing wanted to step into an office closely associated with the PAP. Bear in mind, prior to it being politicised, we had Ishak, Sheares and Wee Kim Wee. And I know many people of good standing were hoping to chosen under the old system. Not anymore.
The PAP also has destroyed the culture of public service by monopolising the process and their tainting of general public service by such things as grassroots politics and favours to mates.