Even at half price this is still quite expensive. I have excellent results from using a mug (approx. 250 ml) of white vinegar on the top rack and putting a quick 35 degree cycle on (empty apart from the mug of white vinegar).
Then , I sprinkle some soda crystals (about two thirds of a mug) across the bottom of the dishwasher and put on another empty cycle , this time the hottest one (the hottest temp. on mine is 70 degrees)

The vinegar acts to degrease the machine and pipework etc , the soda crystals clean out any gunk that is left behind.

DO NOT mix the white vinegar and the soda crystals and try and do this in one cycle as they will react together and the results will not be good !

This is a very cheap way of cleaning the dishwasher and with PERFECT results. Works out at about 55p for me (including the electric usage for an extra cycle) but could probably work out cheaper if you buy bigger quantities.

White Vinegar (purchased from Home Bargains) at 99p for 750ml

Soda Crystals (purchased from Home Bargains) at 59p for 1 kg

Same price in Waitrose. Hewt added

£1.75 if your passing Wilko