I don't know if you have an Albertsons where you are, but I just saw an ad in my Sunday paper that included a photo of all their different party trays. Fruit, veggie, deli spirals, cheese, Mediterranean, etc; they actually looked really nice and we're priced around $20 and up. Costco and Haggen also have similar trays. We're planning to do meatballs (costco), salmon spread in phyllio cups, fruit tray, veggie tray, and then a cheese, spread and cracker tray for about 90 people. Keep in mind you'll need a way to keep items hot or cold before and during service.
If you have a Sam's Club in your area, they have tons of veggie platters and meat/cheese platters. All you would need are some crackers for the platters. Meatballs or spinach balls would make good finger foods too, and they're easy to make.
Shrimp cocktail isn't the cheapest but it is incredibly easy. My boys dream about deviled eggs, a very cheap option. Otherwise, I love the other ideas!
Re: Easy, inexpensive appetizers
Bruschetta or chicken salad on toast squares
Meatballs
Chips and dip