Unless you’re attending Heidi Klum’s famous annual Halloween party where everyone goes all out, it’s probably a bad idea to spend your savings on an elaborate costume you’ll wear once. If your invite got lost in the mail like ours did, an affordable cheap halloween costume (that’s still ridiculously cool and stylish) will certainly suffice. So, how affordable are we talking? Think: the price of a couple lunches or a really nice dinner. From a…