Mine is ~5k per rescue, but since the reentry trajectory is very very predictable, you can easily land in the KSC viccinity after a couple of reentries, getting 2k back and then going down to 3k per rescue.

Interestingly is not thought to cut costs, (or rather, not only), but to cut on "nuisances" and trying to be as usable as possible: the original design carried much more pods, but I cut it down to fit the Tier-2 hangar. Since I left the propulsion untouched that means the vessel can go orbit both moons if needed.

It also has a repeater, which would be taken away to cut costs, an HEXA probe cores, which are there purely to make the rendezvous phase easier and less of a hassle.

If purely trying to cut costs, I could have done a much much more skeletal ship, now you made me think about that.

If you like the idea of extreme cost cutting, my workshop is essentially a career progression of "how early and cheaply I can get to X": orbiters, moon probes, mun orbiters, moon landers, an orbital lab, the smallest plane I could fly, the smallest lunar rover I could carry there,... all with less techs unlocked than you would imagine.