Before reading:
VERY IMPORTANT POINT: you must NOT put the soda crystals in the salt reservoir, they HAVE to go in the tablet/powder dispenser!
Once a month, I fill the tablet/powder dispenser with Dri-Pak soda crystals and run it on it’s hottest cycle (in my nearly 13 year old Lamona that’s the intensive 70 degree one). After the cycle is complete, I give the seals and drop-down door edges a wipe round, and check that the filters are clean.
A 1kg bag of soda crystals currently costs £1.25 at Tesco, the actual weight that fills my dispenser is 30g - so just under 4 pence.
I plugged my dishwasher into an energy monitor plug recently, and running the intensive cycle worked out at just over 1 kWh, so 34 pence in my case (plus water cost).
My dishwasher gets used 2-3 times a week on the eco setting, and occasionally an intensive cycle for oven racks. It’s always super clean, and the filter never has any greasy deposits.
Absolutely no residual smell, just a clean machine.
Have read that you can also put a cup of white vinegar in a bowl on the top rack for the same effect - haven’t tried that?