Check the LH website
(Summary: 1st piece to 23kg:free. 2nd piece to 23kg:€75. To 32kg: €125. In the absence of a sliding scale a la Air NZ, further pieces appear to cost the same per unit.)
If you're thinking airfreight, factor in the handling charges etc and the costs in time and transport to deliver and collect from what is usually the a**hole of the airport....