A local antique store had some feed sack material in plastic bags. Each was priced at $16 for one sack which seemed high to me. Is that the going price?

I would suggest you check Ebay ? And check the condition of the bags and how many are in the bag

I checked EBay and they were less expensive there. These appreared to be complete bags still sewn together. I'll take one out it's bag next time I up where the antique store is.

I would not pay that much.