Food. To throw an inexpensive Super Bowl party, cut down on all the food. Spaghetti is an inexpensive and hearty meal, as is chili. Or, ask guests to bring their own dish to serve potluck style.
Drinks. Super Bowl just isn't the same without beer, but alcohol gets expensive. To throw an inexpensive Super Bowl party, ask guests to bring their own beer. You can also provide a pony keg of beer which is often less expensive than cans or bottles. To really help make it an inexpensive Super Bowl party, consider charging guests a few dollars for a bottomless cup of beer. Keep in mind the type of guests though, as this isn't always an appropriate option.
Decor. Skip it. Seriously, your guests are coming over to watch the game. They will not bat an eye if the house isn't adorned with football paraphernalia. If you must decorate, chances are you have team gear already. Make it an inexpensive Super Bowl party by decorating with items you already have like foam fingers, team towels, or flags.
Skip it. The most inexpensive Super Bowl party, is one that you don't host. Take up friends or coworkers on invitations to their parties. Or, hunker down in a nearby sports bar to watch the game. Though bars can be expensive, chances are, it will be an inexpensive Super Bowl party venue than your own home.