The cost breakdown is about $1.17 to make homemade compared to about $3 for generic detergent.
How does it work? Well Amy from Homestead Revival explains that it is not a one size fits all type of thing. I feel that is very true. She said she used 1 and 1/2 teaspoons per load and I found that 1 and 1/4 worked a bit better in my dishwasher. It is something that needs to be played with a bit in order to get it to work well for you, but I truly feel it will work.
I did notice that it left a dullness to plastic items but the new commercial stuff does that as well. Here in Michigan (and many other places) mass producers of dishwasher detergent have been transitioning to phosphorous free soap. This has been making my dishes dull and sometimes doesn't clean as well. I consider the homemade stuff to work better than the new mass produced item.
As for time. It took me a total of 5 minutes to place it in a jar and shake. That was opening the boxes and getting out measuring cups. I will say that I had a hard time finding the Arm and Hammer Washing Soda at Wal-mart but I was able to find it at Meijer. I checked out the prices on Amazon and I would tell you to just go to the store. The prices online were MUCH higher without the cost of shipping. When that was added in you could buy one box at a store about 3 times over for the price they were charging on Amazon.
I feel this is certainly a recipe that is worth your time and energy to try. The cost is not outrageous and if you don't like it the supplies could be used for other items.
Let me know if you have tried this and how it worked for you.