My 2WD Rustler ST's use the ProTek RC 100T servo. It is a full size, metal gear servo w/25T spline for servo horn. Fits your budget target $49.99.
Torque averages out at 194.5 oz/in. Published specs are 216 oz/in @ 6.0v and 173 oz/in @ 4.8v.
Good luck. Hope this helps. 'AC'