Using tracks is a proven, brute force method of climbing stairs, but is not very cheap. Every gram increases the power required by the motors substantially. The motors
are going to be about $50 each, for a total of ~$100. You can get a sense of just how much torque you'll need using the Drive Motor Sizing Tool
. The microcontroller will be about $30 and the motor controller for these motors about $90 - already you're almost at $250 and still need a battery, tracks, sprockets, frame etc. and shipping / taxes. You would need to make your own tracks (perhaps using bike chain and sprockets). The better option is to make the robot a lot lighter.