All reduction buildings add their deduction percentage to that given by Pulley, Geometry and Spirit Level. This means the actual discount is an additional 1%per level of the reduction building, plus the reduction from the level of research you have completed. For example, a Level 1 reduction building combined with Pulley has a net of 3% reduction, with Geometry there is a net of 7%, and with Spirit Level there is a net of 15%. With the maximum level of reduction buildings (Level 32, 32% reduction) and Spirit Level (14%), the maximum reduction for that resource is 46%. This means you use only 54% of the original cost.