Loft of down can be anywhere from about 300 to 800 cubic inches per ounce. Loft of down is probably the largest factor in determining the price of a down product. Generally higher loft products will also last much longer as the down has grown closer to full maturity and its filaments are much stronger. Lower quality loft products have weak and brittle down and will require replacing much sooner.
Check out this infographic, The Lowdown On Loft!