For myself, i went thru the process of applying for the PR in December 2021, did the interview in April 2022 and finally received the approval of my PR in March 2023 and have collected it in early May as i had booked my family visit already. The amount of paperwork is quite substantial, but if you have a secretary and a HR person of your company helping you, you dont really need a firm or agent to help you. Imo, the HR person is more important, as many documents to support your application come from your work place, with which an outside agent can not help you with. And neither can they help with the document you have to get from overseas. Personally i have not received any request for money from the immigration officers other then the application fee and the final 95K once approved. Anyway, that was my experience.
With kind regards,
Ant.