You know how everyone says they've eaten on their fine china twice since they were married five years ago? That's because they remembered to buy everyday dinnerware! Dishes, even really cute ones, aren't that expensive and come in sets that are great gifts for guests to buy for less than $100. Other pieces like your everyday veggie bowl, bread plate, salt and pepper shakers and other items make great, affordable gifts, too.
The same goes for barware. The $80 hand-wash only glass is less likely to come out for a Thursday night dinner than the $25 box of four wine glasses. You'll also want margaritas, beer, martinis or sweet tea, so register for tankards, margarita and martini glasses and pitchers. Look also at serve ware, like serving dishes, chip and dip bowls and cheese boards to go along with those cocktails.
Register for things to go around your house. Beautiful silk plants might be an expense you don't make a priority, but they're a great price for a guest to select for your gift. Silver candlesticks are a luxury, but they can be ornate and must be polished. Register as well for some candlesticks that match your informal china or your colors in the dining room.
Figurines, decorative votive holders (maybe even in your crystal pattern), bowls and flower vases are perfect gifts, as well. Add them on!