To manufacture one is probably very expensive. However, the equipment setup that it takes to produce one needs a very small amount of new materials to produce the second. I imagine nail files are produced 100,000 or so at a time, at a very low unit cost. I would place it under a quarter each. I’m a guy, so I don’t have any idea what nail files cost at the store, but I can’t imagine it’s more than a couple bucks. So, take your quarter, add in packaging, shipping and tariffs, and $2.99 is looking like the right price to me.