The nation of Fiji is typically thought of as being very expensive to visit, but that doesn't have to be the case. Sure, there are resorts that cost upwards of $1,000 a night, but there are also hostels, dorms, and guesthouses that can be found for $25 a night. It's all about your expectations.
Additionally, transportation around the islands is inexpensive, and all of the beaches are free. In other words, it’s easy to spend a lot in Fiji, but if you're smart, you can experience everything affordably. The only major expense that is unavoidable is the flight there, which varies depending upon where you're taking off from.