I've just remembered we've got a self loading mixer that we don't use much big old lump of a thing. Mixes a cube at a time fill hopper with 3cx then hopper lifts up to fill the drum.
Nobody round here give you a per cube rate on any less than full load. The volumetric firms want a specific amount to give you a quote. Then it all changes based on how little. Years ago it was set price per cu. Different rates if above or below 3m from memory.