These fares are ticketed as both Qantas and Emirates, but all flights are operated by Qantas (Emirates is a codeshare partner). As these fares are less than half of the usual price ($450+), there is a possibility that they are error fares.
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There is also a $194 in there via Virgin. I'd definitely say this is a price error. Don't know much about Gotogate but says they have an office in Melbourne? Wonder if thats legit or just a virtual office.