I spent less than $500 in total, I think, most expensive was the stepper motors and linear bearings. I just use threaded rods as lead screws and it's all constructed from wood.
I'm planning to upgrade it with proper lead screws and a more sturdy aluminium construction so I can speed it up. It can run a lot faster, but it's not stiff enough, so the precision goes down when speed goes up. I just stick to a slow speed for now, works fine and I'm not really in a hurry, just set it up and let it run.