We've found you can actually do a lot with dumb servos and orientation feedback and get visually similar results to Spot. For instance, we get hopping, trotting, strafing, turning + strafing, walking. What it can't do is prancing or a flying trot. But we think it's totally worth it since a good-enough servo is around $20, while similarly sized torque-controllable servo (excluding dynamixels, which don't actually have torque control), runs about $400 each. DJI did actually come out recently with their M3508 and M2006 which we're starting to play with, and we think we can build a torque-controllable pupper for about $1.5k.

The main limitation I think for servo robots with kinematic (position-control) controllers is speed. We're moving around 0.8m/s max, while the new Unitree A1 is something like 3.5m/s.