After about 6 or 7 years working with beads, I have a similar
problem...too much stuff.
You don't have to count every bead, but it is important to be able to
tell how much you paid for material so you can price your work
effectively. For taxes, you can do what is most
effective/efficient/accurate, without going overboard. If I buy by
weight, I keep track by weight. If i bought 250g of beads for 35.00
and I have 125g left at the end, then I record 17.50 into inventory.
You shouldn't have to take a physical count every year though. it
takes a bit long, but I try to record the components price when I
finish the piece. For example, I keep the beads in plastic baggies.
I mark the baggy with the price per bead (including transportation
costs like shipping). When I finish the piece, I count up the price
per bead on the components and mark the total cost on a tag. I tag
the piece with a number and then record the number on an invoice
with cost and corresponding retail price. This is a good system
theoretically, however, when the gallery calls and says "we're out,
we need things right away"....I get freaked out, stop counting and
just send things out. I have faults, what can I say? I will be
attempting a physical count this year.