Prices for the various Q's bottomed out about 3 years ago. KEH usually
has a selection of them for pretty good prices.
They have some unique attributes that contribute to their (limited) popularity:
1. Leaf shutter lenses with built-in ND filters (01, 02, 06, 08) with 1/2000 flash sync
2. Easy to adapt almost any lens ever made, including C
and D mounts with full frame coverage
3. Image stabilization for almost any lens ever made
4. Telephoto capability that is long
and fast
and compact
and has greater depth of field at any given field of view compared to FF
5. Macro capability that is very compact
and has greater depth of field at any given field of view compared to FF
6. Fish-eye lens (03) that is about the size of a spool of thread (and weighs about as much) that focuses to 1 inch
7. True ultra wide zoom (08)
8. Non-intimidating form factor
9. Can be worn on a wrist strap effortlessly
10. Full featured menu is consistent with other Pentax products
11. Leaf shutter adapter for modern Pentax lenses
12. BSI sensor capable of producing quality images
The only other comparable compact ICL camera system is the discontinued Nikon 1
which had limitations in most of the areas listed above and was much more expensive.
Various point and shoots have some of these features that may even out-perform the Q in some areas,
but not all of those features in one package.
Some M4/3 bodies are as small but their comparable lenses are bigger,
generally slower and more expensive; the faster M4/3 lenses are much more expensive.
It isn't the camera for everyone, and it is
not for photographers who must have an EVF,
but it is a useful and versatile tool.