Well, if you know how they are manufactured, it would be easy for you to understand the cost factor behind them. Typically, they are made of waterproof material and a wrinkle-free fabric that can hold water weight. Lastly, the stitching and finishing are durable enough to withstand the elements. Simply put, bikinis are crafted to the highest standards. Thus, they come at a high price. However, all of them are not on the higher side in terms of pricing. The price vary hugely based on the brands you go for. You can find cheap to more expensive options online.