I bought a TV last week. I went there today & it was cheaper this week. Can I get a refund on the difference?

Yes you can online

Yes, they will always credit you the difference (within 30 days of purchase). This one of the great things Costco does. Takes worry of pending promotions out if the shopping picture.

Yes

You can within 30 days of purchase. Have your receipt and membership card with you. This is for in store purchases only.

I would bring your receipt in with the TV they should honor it