There's been roughly a 4:1 price range in lead and 2.5:1 in tin
over the past three years. Currently tin costs about 10x as
much as lead, so you'd expect about a 10-11% price difference
due to cost of the metals. At current prices there's around $5.30
worth of metals in a pound of solder, of which only 30 cents or
so is lead. There's also the plastic spool, the cardboard box
and 10-15 grams of flux.

The fog is lifting...