Sydney, September 24, 2026, 09:28 (AEST) RBC Capital Markets estimates about A$6 billion in extra federal interest costs over four years. That equals roughly 4.1% of the May budget's A$146.22 billion cash-interest baseline. The Reserve Bank's September 29 decision is the next near-term test for yields. Australia's debt-interest bill is headed for a multibillion-dollar increase…