It depends on how much of the wedding expense the couple covered. Another factor is if you are buying individually or as a bridal party group.
If the couple covered the cost of your wear and accommodation, a gift starting at $125 and above is perfect.
You will get very impressive gifts from that price up to and shows gratitude to the couple.
If you are buying as a group, $100 combined by each of you will get a really pricey gift. One that will get noticed.