It could even be more affordable than that too, if you were upgrading a current SRAM mountain bike groupset. Buy a $190/205€ 90 derailleur, $50/55€ 90 shifter, $30/35€ 70 chain, a $215-250/ ...

SRAM Eagle 90 Mechanical Transmission mountain bike drivetrain Review: finally a simple, affordable, tough & serviceable MTB groupset ...