£4595 for that monocoque sounds steep to me - real monocoques went for less than that in the auction and I seem to remember this sold for about £600+premium+tax.
I don't agree that 3D printing wind tunnel models is in any way easy. Whilst the external dimensions of the model are the same as those of the real car, the parts have to be designed separately as they have different fittings, are of different thicknesses and have different internal structural bracing. Once the item has been printed, it has to be finished by hand and the model assembled. That is a painstaking process as the parts are bolted onto a spine, which appears to be even more labour intensive to make. Just look at how much work has gone into this upright/hub assembly (sorry, it's n MR01 rather than a 115M):