Pyrography pens don’t cost that much. The variable power supply they plug into, though: that’s another story. Those cost more than they probably should. [td0g] took the plunge into pyrography ...

U2’s 0 to -10 V output is inverted by the Q2, Q3, and Q4 differential amplifier via feedback to U3’s ADJ input, forcing U3 to ...

Depending on the ATX power supply being used, they may be unstable without the load. The project also leaves a lot of room for adding your own hacks such as variable voltage and current limiting.