As both a former monetarily-challenged collector, and a current dealer,
i hope the list will indulge me while i add my two quarters'
(inflation!) worth on this topic.  Most dealers in countries where their
overhead costs are relatively high (shell storage space, heating, costs
of equipment and supplies, printing and postage costs, etc. etc.),
simply cannot afford to list very inexpensive items, since the profits
realized from them are so small it is not worth the time and effort
involved.  It takes the same amount of time, effort and list space to
sell 50 $1 items as it does to sell one $50 item, so even if one does
lose some business by having a "cutoff" price threshhold below which
they are unwilling to go, they save much time and overhead costs
by doing so.  This may seem harsh, but it is simple economics.  There
are, however, remedies for the collector with limited resources- 1)
dealers in some countries such as the Phillipines can afford to sell 35
cent shells.  I recommend Manuel O. Montilla , for example.  2)
Trading!!  This can be very rewarding, and many collectors have added
substantially to their collections in this manner.  It can be very
time-consuming,  sometimes dissapppointing, and requires considerable
effort,  but  once one finds a few good trading partners, can bring a
fair return, and is also a great way to make friends and contacts around
the world!), 3) consider purchasing sets of less expensive spp, which
show the species' variation to good advantage (something i like to
offer!)- your "species list" will grow more slowly, but your collection
will be more interesting in the long run, since most relatively common
spp have excellent variability, and one or two specimens simply cannot
capture their "essence" (ie, their  true nature- what the species is all
about!)., and 4) less-than-perfect specimens of species they could not
afford otherwise.  I (ie "Schooner.."), as well as many other dealers,
like to offer specimens of more expensive spp which have one good side
for dislay, at extremely reasonable prices.  If one has two of these
which show opposite sides nicely, one has an excellent diplay of the
species, at less than the price of a single gem or near-gem specimen. 
Also, many specimens have only a rough lip, or a bit of spire erosion,
or other small problems which do not signifigantly reduce their overall
attractiveness, but which DO considerably reduce their price!!  To
equate beauty with perfection (ie, to think that ONLY specimens with
very high physical quality can be considered beautiful)   is an error
only those who are weallthy, or those who want to have a rather small
collection, can afford.  It is true that some people can look at a shell
with a beautiful pattern, vivid colors, and an interesting shape or
sculpture, and see only the flaws present, not the beauty.  However, for
me, beauty is wherever you find it, and if you find it in a non-fatally
flawed shell, it costs a whole lot less, and is *still* beautiful!! 
 
                                                                                                        -Ross Mayhew.