Check out Petoi Bittle robot dog(https://www.petoi.com/products/petoi-bittle-robot-dog) for under $270. It has a complete set of tools for entry-level robotics. The motion controller is a Arduino-like controller and can connect to many third-party sensor modules such as camera, gesture & microphone. It supports C++ and Python API
It runs on open source software OpenCat and can integrate with Pi or ROS.
