Costco are doing a 2x90 pack of Finish Classic d/washer tabs for half price until 13th June so that the usual price of £17.61 is reduced to £8.80 which works out at less than 5p a tablet.
My dishwasher came with instructions not to use tablets - yes it's few years old now but still going strong! - so I have been using powder, salt & rinse aid since day one but keep a few tablets spare in case I run out of powder. The powder is also usually much cheaper than using tablets but at this price I've bought a couple of packs and will use them instead of the powder for a while.
I know that not everyone that reads this is a member but a fair few are and the coupon book that I assume everyone received recently didn't state the price.