Not worth it at the dollar store: dishwashing liquid
In order to sell brand names for a $1, dollar stores are reduced to selling these products in the smaller bottles. Thus, a 10.99 oz. bottle of Sunlight dishing liquid isn't as cost-effective as the larger bottle in most supermarkets. I saw a 32.123 oz. bottle of Sunlight for $1.97 in my neighborhood grocery store. That's more than 21 oz. more soap for an extra buck. No contest.
Buying the off-brands will get you still more for your money. In my experience, store brands are often just as effective as the name-brands. So drop the name and clean up for less.