ORAC,
All makes sense - especially the bit about the country that wants the probe paying for it.
Considering that the A is the cheapest model - to both acquire and operate - any cost delta between the A and the B could (presumably) comfortably cover the NRE for the probe for the A. The UK could even make money on the deal by negotiating a royalty into the CCP/ECP that any other country opting for the fitment of the probe, similar to that negotiated by Australia with the Hellfire missile integration on the Tiger helicopter.
My response was more aimed at the snark (not yours) to the effect that "only LM could do the NRE" as if it was somehow unreasonable that the OEM execute - and bill for - NRE on its airframe.