how do they make money on A380 flights to Sydney? flights I've been on had very few
 

how do they make money on A380 flights to/from Sydney?

while my experience is limited to 3 flights on this route, all 3 flights were
no more than 20 to 25 percent full. On one flight, I only counted 57
passengers(myself included) in economy. I had no idea how people
were upstairs in the premium cabins, but I only spotted a dozen or so
during the boarding process.

Not that I'm complaining or anything. There's nothing I live more than
flying on nearly-empty planes. :)

I'm guessing they make money from the full flights. Just a guess. :)

As you suggest, 3 flights isn't representative. EK have somehow managed to fly all types of aircraft profitably, with the possible exception of the 340 recently.

how do they make money on A380 flights to Sydney? flights I've been on had very few
 

I think, EK and other middle eastern carriers have a slight advantage when refueling at their hubs over say EU, Asian and US operators in that one of their biggest OpExs is considerably cheaper!! Av Gas ain't cheap but if you're able to get it at a cut price rate, my guess is this more than makes up for low load factors.

I am just guessing....but last time I was there, even at retail price - gas was pretty inexpensive! !

Carriers from oil-producing countries have to pay
for aviation fuel at their own country's airport?

Ah this old chestnut again,
A: Dubai has very little oil
B: Even if they had the oil they have no ability to refine that to JetA1 (not avgas which only runs piston engined aircraft)
C: All airlines at DXB buy their fuel from 3 suppliers at worldwide rates negotiated by each airline

Most EK flights out of SYD even trans tasman go out with high loads.

You must have got lucky.

There is no way EK would do over 60 flights a week to Australia if they are not profitable

adampenrith has pretty much nailed this.

The occasional 'empty' flight is just a fact of life for any scheduled airline, in the same way that a hotel will have some low occupancy days, or supermarkets will go through quiet spells from time to time.

It's the bigger picture that matters. Most well-run airlines use highly sophisticated yield management systems and historic trend data to get it right most of the time - and (assuming they're quick & smart enough) make changes once any alarm bells start ringing .....

EK has had load factors across the network averaging around 80% for last year so those factors are pretty high.
The guy in charge of yield management is an ex LH guy who jumped ship a few years ago. Thing is if you don't see other flights on the network its hard to gauge. There are flights which are consistently overbooked. BHX for example 2 days ago - 21J/386Y with a config of 42J/386Y.
All they need is a few of those and bob's your uncle it makes up for a light load on a SYD flight.
Sub continent flights are nutritiously always overbooked with a dollop of more overbooking on the side.
Earlier in the month I did an IAD to put me over the Plat threshold and config was 8/42/304 with a load of 6/22/120 so its give an take. The F and J trips are where airlines generally make their money. The bombay special for 1000aed return are few and far between and there is no money to be made on that, but the 8 hours before departure F ticket at like 5-6k aed will certainly be a money maker.

For those whom also say EK does not get cheap fuel - well EK does 'tankering' very well. Flying to KWI on minimum, tankering the aircraft at cheaper prices and then dispatching this aircraft on return on a ULR. Cost saving per trip can be over 10k USD.

according to the Nat Geo docu they fly daily and it's always full usually with connection passengers from the UK

Seasonal variances in loads occur and can depend on the direction of the flight. I cannot give any particular examples with time frames, but I've seen DXB-SYD leave with a 50% LF but the return SYD-DXB will be overbooked. This happens at all airlines, nothing special to Emirates.

If the flight is vastly undersold they sometimes cancel the flight - it's happened to me twice now.

That's highly unlikely in the case of Australian flights as the A380 gets a high utilisation rate with EK, not to mention the issues of crew roster (crew that flies on day 1 will command the return flight on day 4).

To answer the OP. It's all to do with 2 things:
- It's revenue (sales) over a period, not per flight (rendering the service).
- Cargo. EK has tremendous cargo capacity in/out of Australia which is pretty much sold out. I once heard that their flights can break even on cargo contracts alone. Whether that's the case I can't confirm (it costs a cool 250k dollars in fuel to take the A380 on a 14 hour flight).

Just to add to the 'EK gets preferential rates on fuel' argument. That's just utter nonsense. It's like saying QF pays less in Australian taxes because it's Australian. And guess what, Australia is an oil producing country too (at around 10% of what the UAE does 240k barrels/day vs 2400k) and yet we don't see QF, VA, or any other Australia airline getting 'preferential' pricing on jet fuel (which is produced overseas from what I know).

Also, the argument seems to ignore the fact that an aircraft is refuelled at both ends (e.g. at DXB and SYD) as they can't just carry fuel for a return trip even if it's cheaper at DXB (it isn't).

Most fuel products, whether aviation, marine or ground transport, are traded and priced against international benchmarks (most contracts use the Platts benchmark, which is based on assessments of reported deals). Variances occur according to quality and quantity versus the standard Platts definition, plus location-driven adjustments and agreed forex formulae. That's about it, regardless of company status or the country's oil supply length or shortage. I've made a pretty complicated formula as simple as possible, so I'm sure someone will point out something I missed, but the basics are correct.

The OP's experience is just chance.

Every time I've flown EK between NZ and DXB (via SYD, BNE or MEL) each leg has been full or nearly full.