Emirates Skywards - Flex ticket quirk in need of one way for mile run

I have a flex ticket in 3 segments
LHR-DXB
DXB-RUH
RUH-(viaDXB)-LHR

Between the first and 3rd segment there is about 1 and a half months. When I try to date change the DXB-RUH sector it comes up with a total charge of £75. When I change the routing to say DXB-JNB its £87 to change and even when I change the routing DXB- SYD it comes up with £190 to change. So this means I can take a very cheap mile run provided I can get a good one way return portion (e.g. SYD-DXB or JNB-DXB).

The only restriction (i.e. the booking system does not allow it) seems to be going westbound (e.g. Europe/USA).

As the outbound leg is going to be quite cheap, to make sense and miles per $, I need a very cheap one way return.

Any thoughts on:
1) this booking quirk
2) ideas and experience on a one way from eastern hemisphere to DXB (happy to look at non EK flights too)

It isn't a quirk, LHR-RUH is just an extremely overpriced route.

For example, I'm seeing LHR-RUH to be around 600 - 800 GBP (random dates in June). LHR-SYD is bookable at around 1000 GBP.

If I try LHR-RUH/SYD-LHR it also prices out to about 1000 GBP. I could be looking at higher/ lower fares on certain dates, but I think if you want to do an MR, change both outbound and inbound to SYD and book an Airpass to go to and from RUH.

Thanks ung1 - you're right, it is overpriced. Managed to play around with routing and got dxb-akl into the routing for an additional £350. Might stick to that as the mile run portion.

Thanks for assistance.