$500? Stole it. You can't build an SP1/M16A1 replica now for under $600 and you have to get a good deal on a kit to do it (which are hard to find) and even then with those you're going to get something kind of ugly (though mostly functional) like mine. Those SP1s are regularly over $1000 anymore. When you get one in your hands with a pencil barrel you realize how light the gun was and how handy it was to have around, not like today's guns with HBARs and 4 pound rails hanging off the front.