I did my cert iv thru work at the bosses expense..(non aviation job)..
Was a piece of piss to get the certificate... the trainer came to my workplace for about 5-6 half days, studied a little bit at home, then tested/assesed me on-site and i have my certificate.. Its pretty straight forward...but I would imagine most of the cert iv items would be covered in an instructors training course anyway....
You can also do this training thru Tafe and distance learning which would be a bit cheaper..
Instructors will be even more broke if they have to pay for this certificate on top of an instructors rating! maybe they could try n get the employer to pay for the certificate... yeah right! LOL