Aaron:
 
The Oxford English Dictionary (OED) contains pages of definitions of both 
"by and "to." The "by" definition that may apply is "distributively, for
each, for every."  The "to" definitions include "introducing an expression
denoting price or cost."  In either case, the words in question link the
item or commodity on the left side of the page with the cost or the amount
on the right side of the page.  I usually translate them (to myself, as I 
read) as "at."  For example, "Item: a sute of cloaths at 1:10:00."  There 
may be credit and debit distinctions between to and by, but the context of
the document is a reliable guide to those.
 
BTW, the OED may be the single best resource for documents researchers in 
the Anglo world.  Legal dictionaries may also provide useful information. 
 
Lauren Cook
Staff Archaeologist
Boston Affiliates, Inc.