I used to coach a FIRST Tech Challenge (FTC) Team for my son's high school. The main Robotics competition for middle/high schools are based on the FTC Pitsco TE

I used to coach a FIRST Tech Challenge (FTC) Team for my son's high school. The main Robotics competition for middle/high schools are based on the FTC Pitsco TETRIX, FRC AndyMark, VEX Robotics Platforms. You can find the majority of hardware and electronics you need for basic robotics from the following sites: https://www.pitsco.com/ https://www.pitsco.com/ https://www.vexrobotics.com/ https://www.vexrobotics.com/ https://www.andymark.com/ https://www.andymark.com/ http://www.revrobotics.com/ http://www.revrobotics.com/ https://www.servocity.com/actobotics https://www.servocity.com/actobotics The high costs come into play when you have to deal with high precision servos with high torque. The Trossen Robotics site gives you an example of high precision servos and pricing. https://www.trossenrobotics.com/ https://www.trossenrobotics.com/ You can find cheaper robotics options at the following site https://www.robotshop.com/ https://www.robotshop.com/ When you run a team you start with a budget in the low Ks and build out the equipment inventory over several years. There is high attrition in many of the electronic parts (Servos, Controllers, Sensors) when you compete. Building basic robots is not complex. Basic navigation using techniques such as dead reconing, etc are not complicated. What is complex is advanced software techniques for navigation, motion planning, etc which rely on some complex math. Have Fun!