Some things the list just loves, the right books, the right software, and
the right hardware from teeny bits to whole systems. Price is very often a
major factor, that and clarity of the deal (it what you really want for the
item, with payment and shipping terms). Make offer, or trade for some odd
part, has a MUCH lower chance of a response.
Other items do well on eBay.
Other items do well only at live events like VCF.
Most of the time squeezing the last dollar of retail value out of an item
isn't worth the effort, and I am often happy just to know something is
being used instead of sitting in a landfill.