X-ray luminosity ([0.5−2] keV band) vs. mass for our sample (left-hand panel) and the new Planck clusters (right-hand panel). Masses for Planck clusters are Y_X-based, whereas they are caustics based for XUCS. The solid (red) and dotted lines are the REXCESS Malmquist-bias corrected mean and mean ± the estimated scatter. The long dashed (blue) line is the mean REXCESS scaling offset by 0.3 dex describing the lower envelope of Planck clusters. Several XUCS clusters are below this envelope.