A bit of my Excel modelling summarised for the benefit of all.

Suppose you are aiming for QFF Lifetime Silver (7,000 SCs) or Lifetime Gold (14,000 SCs), which you will be doing entirely on *ONE4. You want to minimise the lifetime net cost, after allowing for reward miles, but you don’t care how many *ONE4 trips it takes (i.e. you are not interested in getting to places for their own sake, yes, a debatable assumption, but maybe not in this forum), or what cabin class you are in (yes, another debatable assumption, but bear with me). You have a lot of free time. So you are tossing up between MONE4, DONE4 and AONE4. By the way, to reach Lifetime Gold in this way, you will need about 27 MONE4, or 7 DONE4 or 5 AONE4.

The GROSS cost per SC is highest for a MONE4. DONE4 and AONE4 are both better value per SC. But the miles earned while getting a given amount of SCs are much better on MONE4, (because it takes many more trips) even after allowing for 25% earn in discount economy on BA and 50% earn on AA discount economy, and after allowing for the cabin bonuses (25% D, 50% A). Depending on what value you place on the reward miles, on what status you are while accruing them (i.e. how many of the MONE4 per year you do), and to what extent you use QF (including codeshares), BA and AA, the net total cost can actually be lowest on MONE4.

Anyway, according to my humble calculations, which, despite my misleading FT name, are in no way authorised by QF, if you are WP while doing your MONE4, travel 30% on QF and codeshares, 20% on BA, 20% on AA and 30% on CX and other (with no status miles), and if you value your reward miles at Oz 4 cents or more per mile, then the net cost is less for a MONE4 than for DONE4 or MONE4. If you value your reward miles at less than 4 Oz cents per mile, then you should stick to DONE4 or AONE4.

All subject to the assumptions in the first paragraph.

By the way, if you value your reward points at 5 Oz cents or more, the net cost is actually negative in all classes if you start in CAI rather than in Oz. BKK is negative net cost at about 7 Oz cents per reward mile.

No, my Excel spreadsheet is not for sale. I have told you too much already.