Just did a quick search for the 180 APO on eBay and apparently there are quite a number up for sale these days. Nearly all carry a hefty price tag and the asking price might now have surpassed that of the 125/2.5 APO as the latter appears to sell for less than before. The 180 is the rarer lens so once knowledge about its qualities becomes common-place, demand for it rises and with that the price level. I think my sample was purchased > 15 years ago in a time where few people paid any interest to these APO optics and accordingly, asking price was most moderate.
I have plenty of Voigtländer lenses, but only a handful of the APO Lanthars. Four for the F mount (90/3.5 SL.2, 2*125/2.5, 180/4), for Nikon S rangefinder mount the elusive 85mm f/3.5 (which easily is adapted to Sony E or Nikon Z), and the newcomer 65mm f/2 in native Z mount. The 85/3.5 APO for Nikon S can occasionally be seen on eBay (there is a nice unit right now) and is interesting because the price is often half, or less, than that of the more common 90/3.5. It does not focus as close as the 90/3.5 since it is a rangefinder-coupled lens, however it can take extension or close-up attachments. Using Z (or E) extension is the easiest approach as the filter size is a tiny 39mm and some ingenuity has to be called upon to fit most attachments. The 85 is so small it'll disappear in most pockets and weighs next to nothing.
Anyway, an overview of the APO-Lanthars in my possession. From left to right 65mm f/2 (native Z), 85mm f/3.5 + S-Z adapter, 90mm f/3.5 SL.2, 125mm f/2.5, and the 180/4, the three last ones using the FTZ adapter. All except for the 85 have CPU communication to the camera.
Do note the smallness of the 180 APO.