A digital image is a grid of pixels. The dpi value does not add or remove any of them; it only tells a printer how many pixels to place along each inch of paper. The same file tagged with a low or a high value shows exactly the same picture on a product page, because a screen displays pixels one for one.
Some marketplace specifications still name a dpi value beside the pixel size, a habit carried over from print catalogues. Where both are given, the pixel dimensions are what decides sharpness and zoom, and the dpi value is a field in the file that an image editor can set without changing the picture.
Raising the dpi value does not make a small image larger or sharper. An image with too few pixels needs more pixels, either from a larger original or from upscaling, and an image with enough pixels passes whatever its dpi field says, as long as the marketplace does not check that field.