I think the last sub gauge shells, aka 20 ga or 28 ga, I bought were in the $13-$15 a box range when buying at case quantities but frankly, I do not remember exactly. I've well stocked for myn skeet shooting but I've curtailed it some so that I do not consume the supply too quickly.
I enjoy reloading so I buy premium ammunition whose hulls reload more time than the cheap "Gun Club" ammunition.
Unfortunately, in today's environment, getting components is a problem especially primers.
Currently, I'm shooting off some 7/8 oz 12 ga ammunition that I loaded 10 years ago or so.