Business 101 matey.
Correct, that's precisely what it is. Those who have graduated beyond business 101 would know that low fares mean absolutely zilch unless they're matched by capacity, something that Tiger doesn't (currently) have. They either have very few seats available on city pairs, or don't operate the pairs at all! No J* don't have to compete on a larger scale. Jetstar certainly do "match fares" on the few routes served by Tiger, but I defy you to actually book one of them. Smoke and mirrors me lad, don't get sucked in by the headline fares as their target market constantly do, I suspect you have far too few hair braids and dead
VB cans laying next to the computer for that.
Regardless, I don't want to get in to an argument over it, you're free to believe whatever you like, and if you believe Tiger is making such a massive dent to the Qantas Group's bottom line, go for it. What I'll say is that isn't happening at the moment and possibly never will. The Singaporeans certainly believe differently and since it's their cash they're burning they can do with as they please. Given that they didn't pull out of Australia when most thought they would it's clear they're committed to the Australian market.
Edit: Just to elaborate on the above and make it clearer still what I'm alluding to. Imagine I began "Squark Airlines" operating a Cessna 152 RPT between Avalon and Adelaide. Humour me on the legalities of trying that. I sell my one available seat for 1 cent. "Business 101" would then say that J* will match the fare on all its flights between Avalon and ADL. But of course if it does it matches the fare AND the capacity ie it also sells ONE fare at 1 cent and proudly announces it's matching "1 cent fares". What's it done to its bottom line, absolutely nothing, nor has "Squawk Airlines" done anything to affect the fares on all the other destinations not serviced by my proud little 152. Smoke 'n' mirrors!