Saving money on dish detergent

I have a dishwasher, much to my dismay.  I hate dishwashers, but that is another subject.

I previously had a 99 cent (12 ounce) bottle of Dawn that seems to be diluted down.  I decided to buy the (24 ounce) Ultra Dawn for $2.50 on sale.

My mom, who is 91, thinks more is better and likes to squirt about a tablespoon of detergent on a coffee cup to clean it and then use about a gallon of water to rinse it.  lol

So, I decided to use the diluted Dawn which was less expensive.  Once it was empty, I put about 6 ounces of the Ultra Dawn in the 12 ounce bottle and filled the rest with water.  I now can make 4 bottles of the 99 cent size for $2.50 instead of the $3.96 it would have cost buying each 12 ounce bottle individually.