NETGEAR ORBI AC2200 RBK20 Home Tri-Band Wireless WiFi Modem Router & Satellite Extender System, White, RBK20-100AUS. This is the two pack - one router and one satellite (the RBK23 pack is the same tech but one router, two satellites).
Not the historical cheapest ($233 in 2018) but the cheapest I've seen since the COVID work from home surge has made them scarce. The same pack is currently $399 at Officeworks and Good Guys (non Commercial), $317 at Mwave, and $504 at Amazon.
The even-better RBK50 is $427 at GG Commercial which is higher than 2019 but have seen it in the $500-750 range consistently during COVID. These units are larger, but have more gigabit Ethernet ports, AC3000 and more aerials. For apartments and medium houses the RBK20s are fine. I have used both systems at different houses (some comments here).