BFOD does not necessarily mean "cheapest". There are several factors involved, including operating airline, hard product, soft product, timing, connections, price, and even for that matter FF benefits
"BFOD even with FF program" merely suggests that other factors other than FF program are possibly more important in the calculations.
Yeah - I guess BFOD would describe the choice as only being 3-3 Y class with 30" or 31" seat pitch and assuming all soft products are the same and route network and frequency would be similar across competitors, a sort of quasi-Areoflot situation. In a competitive market, its unlikely that airline seats would become an interchangeable standardized commodity, and different airlines would experiment with different seat pitches/baggage inclusions and soft products like food and drink to differentiate themselves from their competitors.
If there was no variation in the product then BFOD and convenience/timing would be the main deciding factor.
But I think the rather hypothetical question originally posed was that if you removed all the FF benefits and status from the domestic airlines
as they currently operate, and with their current fleet and cabin fit-out as they currently are, then I expect that Qantas might be able to maintain a very thin premium over the middle of the market with things like free food and some free drinks, the middle of the market being Rex and then Virgin, and I would expect that Jetstar would have to reduce its prices. This is a very hypothetical question as the cost base for Qantas would might possibly be lower without having to run large lounges but their cashflows from the frequent flyer business would also cease to exist, but if the labour costs and industrial landscape remain unchanged then Qantas would still have higher costs than its competitors and would have difficulty without a frequent flyer program, especially since they operate the older and less fuel-efficient aircraft and Jetstar operate the newer and more fuel-efficient aircraft.
Aviation has high barriers to entry but fortunately, most markets are competitive, and market participants are inventive in working out how to differentiate their products from their competitors.
I think a more troubling but unlikely hypothetical would be - if you removed all the safety standards of seats and seatbelts and aircraft evacuation rules with the current fleet of aircraft in use and in production, how dense a configuration would the market turn up and how many people could the accountants fit in a B738 or an A320? And at what price point would people be prepared to pay for a seat or even for leg-room?