2 x 100pk Finish Powerball Power Essential Dishwashing Tablets Lemon Sparkle $21.60 + Delivery ($0 with OnePass) @ Catch

Part of the Catch closing down 40% flash sale.

Finish Classic tabs 90 pack $8.64 works out at 9.6c per tab

Finish Powerball Essential with the red thing 10.8c per tab

Free delivery with Onepass.

If you prefer Fairy or other versions of Finish, they have good deals on them too, but these are the stand outs IMO.

Mod Edit: Removed duplicate from title.