Asus Great Singapore Sale pricing (from Challenger)
High-end
GT-AX11000 Pro -- S$759
GT-AX10000 -- S$699
RT-AX89X -- S$699
GT-AX6000 -- S$699 (but you can get BNIB units from Carousell at less than S$500)
Mid-end
TUF-AX6000 -- S$359
RT-AX82U -- S$329
RT-AX5400 -- S$279
TUF-AX4200 -- S$249
Mid-Low end
RT-AX58U -- S$225 (not recommended, better get TUF-AX4200)
Low end
RT-AX57 (new) -- S$199
RT-AX56U -- S$179
RT-AX1800HP -- S$129
RT-AX53U -- S$99 (but you can get better RT-AX55 BNIB from Carousell at about S$80)
Asus router pricing from Challenger website for reference (price dropped)
High-end
GT-AX11000 Pro -- S$629.10
GT-AX10000 -- S$593.10
RT-AX89X -- S$539.10
GT-AX6000 -- S$539.10 (but you can get BNIB units from Carousell at around S$450 to S$480)
RT-AX86U Pro -- ?? (S$429), said to be available in Challenger Nex
Mid-end
TUF-AX6000 -- S$323.10
RT-AX82U -- S$269.10
RT-AX5400 -- S$251.10
TUF-AX4200 -- S$224.10 (recommended, good upgrade from lower end Asus routers)
Mid-Low end
RT-AX58U -- S$202.50 (not recommended, better get TUF-AX4200)
TUF-AX3000 -- S$220.50 (not recommended, better get TUF-AX4200)
Low end
RT-AX57 (new) -- S$179.10
RT-AX56U -- S$134.10 (EOLed by Asus)
RT-AX1800HP -- S$116.10
RT-AX53U -- S$89.10 (but you can get better RT-AX55 BNIB from Carousell at about S$75)
Note: The price is just for reference. I am not good at finding lobangs -- so you may want to check other places as well for better deals (eg: Lazada, Shopee, Qoo10, Carousell, Courts, etc).