I don't know about the price, but helping a fellow unload one and fire it for the first time (at the range) was my motivation to build my 2nd mortar.
My first was beer-can caliber (1974 beer cans - which soup cans are now that beer cans are smaller).
It was a traditional caliber, so the 4"pvc pipe (4.5" diameter OD) was too small. So the connectors for the 4" pipe were used, filled with concrete.
I had mine made of 4140 steel (picutred on the left) and Aramaloy industrial hard chrome plated. (Have about $800 in it, but it would cost $1300 to do it again - I did some trading). Mine shoots 4" pvc pipe filled with concrete.
He can take his to the competitions because of the caliber. I can shoot mine cheaply.
Consider the bore diameter and where/how you're going to use it.