I have a bucket I keep under the sink and when my dishwasher powder runs out I pull the bucket out, dump 5 cups washing soda and 5 cups borax in. Then I put in about 50 drops of grapefruit seed extract. (It doesn't matter how many cups you use, just do a 1:1 ratio of washing soda to borax).
And shake it up, shake it up... Just like Taylor.
I keep a 1/4 cup scoop in the bucket and fill it about halfway for each load. And sometimes when I'm feeling extra ambitious I'll toss in a splash of vinegar before I start the load. And that's it. It's that simple.
I'm not sure how much I'm saving or if I even am, but it saves me from all the unnecessary chemicals in regular dishwasher detergent.