>A $300 lens is objectively better than a $5 smartphone lens.
Not sure where you are getting the $5 figure from. In any case, smartphone lenses are manufactured in vastly higher quantities than lenses for interchangeable lens cameras, so it doesn't make sense to compare the per unit cost. Modern smartphone lenses are miracles of optical engineering. See e.g. https://news.ycombinator.com/item?id=30557578 The cost of the R&D that's gone into enabling their design and manufacture probably couldn't have been recuperated if they were being used only in cameras.
Not sure where you are getting the $5 figure from. In any case, smartphone lenses are manufactured in vastly higher quantities than lenses for interchangeable lens cameras, so it doesn't make sense to compare the per unit cost. Modern smartphone lenses are miracles of optical engineering. See e.g. https://news.ycombinator.com/item?id=30557578 The cost of the R&D that's gone into enabling their design and manufacture probably couldn't have been recuperated if they were being used only in cameras.