I think the eBay label printing is for full parcels with tracking only. You can send DVD case-sized items as what Australia Post calls a "large letter" for $2. As long as it's within 2 cm height. I have been doing it for many years.

Only downside is the no tracking. If you want tracking then you need to go full parcel price or find another option. AP no longer offer the 250g weight bracket for parcels.