While lasers aren’t exactly expensive now days, you can still get creative with the old scrap computer parts that might be laying around. YouTube user styropryo sure did, as this example’s “power supply, multiple heatsinks, and laser diode all came from a computer.” Video after the break.
You’ll just need a DVD burner (16x or higher) some heatsinks and the PSU from an old computer. There are a few other items you’ll need to get, but those are the main components. In a short while, you’ll be able to cut through small objects, and light others on fire.