The four major things affecting the cost of packaged bees are
    1) Supplier
    2) Strain
    3) Quantity
    4) Postage
 
Rule number one regarding suppliers is KNOW YOUR SUPPLIER.  This is a
hard thing for a beginner to do and such knowledge unfortunately usually
comes from trial and error.  Better yet is word of mouth, although when
this perennial question was last asked, list members were reluctant to
publicly denounce suppliers who have been less than sterling.  And it
was also the case that some members were dissatisfied with the very same
supplier who received great reviews from other members.  Imagine a
lack of common opinion among beekeepers - what a concept!  The final
resolution to this issue was shop around and find three or four
suppliers that are satisfactory to you.  You might peruse the BEE-L logs
from this time last year to get some recommendations - there were a few.
 
Strain: Prices differ for different strains of bees.  Italians will cost
less than "Buckfasts" and some suppliers offer hybrids and double
hybrids that will also cost more.  Reasons for this are the cost to
breed the hybrids, royalties paid to the original breeder (as is the
case with "Buckfasts") and supply and demand.  Suppliers offering mite
resistant strains are able to get a better price for their bees as the
beekeeping public is willing to pay more for the chance that their bees
will have a greater chance to survive.  The demand for the claim is high
so the supplier is able to cash in, and if their claim of mite
resistance is true, cash in they should!  Be aware that the only
available mite resistance (as far as I know) is resistance to tracheal
mites, which are a lesser threat than varroa (although still a very
serious problem).  The search for varroa resistance continues and
breeders are working to cultivate hygienic behavior to combat the vampire
mites, but success has been elusive and for the time being varroa
resistance is a claim that should be eyed with caution.
 
Quantity: you will pay less per package if you order more packages than
you will for one or two.  Perhaps you have a beekeeping buddy with whom
you can pool an order.  Although your total order will cost more, your
price per package will come down a few bucks if you order 5 as opposed
to 1 package.  If you can get the quantity of packages way up (perhaps
100) your cost per package will drop significantly.
 
Postage: Costs to ship bees have sky rocketed in the past few years.
You will incur the same cost to ship regardless of who supplies your
bees.  If you are able to procure bees from a reliable supplier within
driving distance you will save a substantial amount on postage.  The key
words here are "reliable supplier".  It makes no sense to save the
postage by driving to "Fly by Night Apiaries" only to have your bees
fail.  If you can't rely on good bees from a local supplier, pay the
postage.
 
So, does this answer the question?  I suspect not, but it does give you
some important things to consider.  As far as what supplier offers the
lowest bottom line, get a current copy of ABJ or Gleanings and check the
advertisements.  Prices will range from mid $20 to low $40 (US dollars).
As far as the other issues, as always, CAVEAT EMPTOR!
 
Aaron Morris - I think, therefore I bee!