You may be assuming this is not deliberate and that they would actually want to change it?

I'm not a lawyer either but I should imagine QR have been doing this long enough and included enough asterisks and T&Cs etc to make a successful consumer claim unlikely (even if nobody has tried one before)

Explanation is in no way an endorsement of course, it is definitely confusing. But two things spring to mind.

Firstly, timing. The cost to buy business when you originally booked is unlikely to be the cost to buy business when the offer comes around within two weeks of departure.

And secondly, these offers are generally priced per sector, just as points and airport upgrades are. You don't get the married segment fare or discount when you upgrade that way.

So they may be able to argue that you are buying and saving against the single sector cash price at that time. AAA-DOH plus DOH-BBB is always going to cost more than your AAA-BBB fare. And even with the small discount for buying both offers, as in the opening post, you are still buying two x single sectors.

Their home market is likely usually buying per sector to or from Doha anyway, so that may be why these offers are structured that way.

It is still possible to fully upfare once these offers come around, but you would upfaring AAA-BBB rather than each sector. So that should be cheaper anyway.

That all said, the upgrade offer prices are expensive, no doubt. But some people must be buying them, and it seems unlikely to be either a mistake or a legal gotcha moment. One of our regular lawyer contributors may be along to give a more considered view in due course though.