It is also possible to use current sensing to measure torque. ODrive + brushless + encoder (~150€ per axis) can provide current measurements, though you may ne

It is also possible to use current sensing to measure torque. ODrive + brushless + encoder (~150€ per axis) can provide current measurements, though you may need to create some PID loop. If the brushless solution is still too expensive. You can use 775 brushed motors + encoder + BTS 7960 driver + (optional gearbox) (They have current sensing by using additional resistance (Edit:and RC filter) ) (10€-50€ per axis from china). Although that's not powerful enough for jumping robots.