No, they are not identical.
The HG bearing case is journal, and this is where the ~$500-$700 price difference comes from.
Where the GCG (for example) are ball bearing case. Garrett Ball bearing cores are around the $1000 mark in that frame size, it makes sense +wheels/balancing +machined housings, makes sense they are then more expensive.
Also note that becoming a SAU-NSW member gets you 10% off GCG turbos