Costco’s camera & photo offers, just like many other products they carry, vary depending on whether they can get good volume discounts. One such good volume discount they have now, restricted to Costco members only, is this Pentax K-S2 two lens kit (18-50, 50-200, case, 32GB SD) for $450, with a limit of three bundles per customer.
With memberships going for $55, depending on whether you need this particular kit right now or not, it may be worth to sign up for a 1-year membership just for the discount of this particular offer.
Some offers can be purchased by non-members with a 5% surcharge. However, other offers are marked as Members Only and can only purchased by actual members. This is a members-only offer.
For general Costco action, there’s the Costco Insider website.