I acquired the T3 receiver and trigger assembly, shown below, for $500. The beautifully machined bolt and receiver are proprietary, but everything else is compatible with the broad market of Ruger 10/22 accessories. The trigger assembly features a crisp 2.5-pound trigger, and is all metal except for the trigger itself and the convenient extended magazine release lever in front of the trigger guard.
I installed the receiver in a Hogue stock. The 18″ barrel came muzzle-threaded from EABCO and button rifled with a 1:9 twist rate: sufficient to stabilize subsonic 60gr Aguila .22 bullets. (The standard .22LR twist rate is 1:16.) Those two components brought total cost for the gun to $750, excluding a scope.