Wow..that expensive?

Hey guys, just asking regarding some slight noise issue with my flx 1.6

Note: I've taken for inspection last week, but the mechanic seems to tell me its nothing.

The issue:
When i off my radio and aircon. I noticed there this sound from my rear wheel, possible left.

There is a slight creaking when I gently tap on my accelerator and when it the momentum slows down, I can hear it again.

Very much like those you hear in cabs. Is it a suspension or shock absorber issue?

Thanks in advance for the advise from the sifus here..

Thanks bro...hope the proton mechanic check fully tmr during my routine 15k serv.