Hi Jhon.
i check your post and see the number dont match, i mean:
Unit cost in CK11N is 2808.03 / 100unit, but in KP26 is 8542.48 + 6577.54 = 15120.02 per 1000 so looks like your Valuation Variant is not using the plan cost in KP26.
Could you check your costin variant in tcode OKKN and check the Activity type tab ? (DOnt forget to chack also at plant level)