I fly this route more than I care to and agree that the EK flights in F are comparatively poor value when purchased as stand-alone DXB-RUH tickets. The crew are also consistently the worst I encounter on my EK runs - although I can imagine Riyadh is fairly low on the cabin crew wish list!

That said, these flights are almost always full in F so you can't blame Emirates for charging what they can. My guess is they need the seats for people they are through ticketing to other destinations on F so try and price the RUH-DXB passengers out of them - my understanding is that they can't add extra flights on the route so need to maximise the return from the limited seats they can offer.