The detergent label usually recommends the highest amount that may be needed, ignoring variables such as water hardness and whether you are washing relatively clean water cups or pans with caked-on grease.
The next time you do dishes, try using a smaller amount of dishwashing detergent than the label instructs you to use. Try half the normal amount. If your dishes don’t quite come clean enough, use ¾ the recommended amount next load and see what happens.
If your dishes do come clean with half the normal amount, you’ve just found a way to save 50% off your detergent costs!
If you do have a load that has more grime than usual, you can always add a little more. Meanwhile, why use more than you need?