2 aspects to this:
QF has, I think, a $60(?) surcharge (or price diff) added on for the codeshare. No idea why but that seems a standard thing.
The second issue that peeps have to keep in mind is that a codeshare involves airline A(in this case EK) selling a set number of seats per service to airline B(QF).. QF sells those seats they have agreed to take from EK at a set price, so they can then sell them for whatever price they want (which possibly explains the $60 thing above, as a profit margin of sorts - though obviously they're not getting those seats at anything close to retain, but it's still going to be relative).
Now given that they do not have the entire plane to sell, only a certain block of seats in each class, QF revenue manages THOSE seats probably differently to the way EK manages theirs.
So for example QF has 100 seats on an EK aircraft holding 500 (this is deliberately not accurate as it's an example of the idea only).. Essentially that QF "flight" has 100 seats, not 500 (or 400). Now while someone who knows more about codeshare agreements can explain further, I am not sure how these things go if EK sells out but QF doesn't (or v.v.) it may be a flexible/% based agreement (and it's probably CiC anyway) but I still feel the general idea holds....
my point being that EK may have a bunch more seats to sell at cheaper prices, with cheaper fare buckets open, but QF may not have those cheaper buckets open on the same flight, thus raising the price per sector.
I'm happy to be corrected on this, but this is my general understanding of how codeshares work.
As an example the other week I saw a QF domestic flight with some seats in J but the EK codeshare had 0's in the equivalent buckets.
Whatever the selling/sharing arrangement between the carriers is a codeshare flight can have different availability (and remember, availability can vary on origin and destination cities too where a sector is included - eg: FCO-DXB vs FCO-DXB-SYD where QF may want to sell/offer lower fare buckets on the connection but limit on the individual city pairs, specially if it would involve a transfer to their own metal).
Again, happy to be corrected.
(oh and as aside, I think it would be rare that EK would sell a QF codeshare on their own metal). You can, of course, book QF codeshares via other TA's not just qf.com but EK themselves would be loath to sell a partner code given the revenue would go to the partner.
my 2 cents