[ARCHIVE ANSWER]
Our economy in general will dictate consumer spending. If energy costs are high, then
everything else will be affected. If consumers aren't buying, then dealers aren't selling
and will carry less. The season and environment also causes dips in the market for
commercial product grown outdoors. Indoor grows maybe not so much.
Also, interdiction efforts in your area might cause dips. If most of your weed comes from
one or two growers, and one got busted, it will get real dry for a while until dealers found
new sources. And if dealers get busted, it will take time for replacements to emerge.
Weed can also dry up because the big dealers at the top want to make a little more money
by controlling the supply and thereby create inflation. At the same time, selective
breeding can now produce little plants that mature quickly and produce huge sticky buds.