Transfering to another broker is discussed in this whirlpool thread here: https://forums.whirlpool.net.au/archive/2698381
From what I'm aware of the $50 transfer fee is if you are transfering your shares to an issuer-sponsored format, which is something held directly with the register of that company whose shares you hold. Not 100% sure and someone please correct me if I'm wrong but this basically means you hold the shares yourself without a broker-sponsor (like IG is) and without a CHESS/HIN (like CommSec or NabTrade).
CommSec has some info here: https://www.commsec.com.au/support/frequently-asked-questions/410.html
From what I gather you just need to submit a broker to broker transfer form with your new broker. It might be a little more complicated because IG doesnt use CHESS/HIN, but I think the process is still the same. If someone knows more please correct me, this is just my understanding from reading online, I'm no expert.