At Costco, members can buy one Finish All-in-One Dishwasher Detergent Powerball Tab 110-Pack for $16.99 and get a second one for free. (Add one to cart; the second one will be added automatically. Non-members pay 85 cents more.) With free shipping, that's $0.08 per tab and $26 under the lowest total price we could find for 200 tabs. (For further comparison, we saw 90 tabs for $6 less three weeks ago.) Deal ends August 31.
Of note, you can buy up to five 110-packs and get five more free for a total of 10 boxes.