The first thing to know is that the price of gold is very transparent. Often the price difference between gold necklaces comes from different styles, brand premiums and so on. Bainianfu brand is a medium-sized brand in China, so the price is relatively cheap and the style is relatively novel.
Compared with some big brands like Chow Tai Fook, it is definitely more affordable. Buying gold usually depends on whether you like that style or not. If you like it enough, as long as it is a reliable brand.