This is part of a study investigating the structural properties of blocks produced from using different combination of laterite and quarry dust as full replacement for conventional river sand as aggregate. The use of alternative materials in blocks production and other concrete works is becoming increasingly popular across most developing countries. This work developed a mathematical model using Osadebe Regression Theory (ORT) for the prediction of cost/cum of laterite- quarry dust cement block. The lack of fit of the model was carried out using statistical tool (excel) and found to be adequate. The model will be very useful especially for commercial blocks producers and built experts in Nigeria and sub-Sahara African countries for construction cost estimation and profit projection.