Greg,
Your current documentation examples for customs scripts in pgbench
includes the variable :scale, i.e.:
\set nbranches :scale
\set ntellers 10 * :scale
\set naccounts 100000 * :scale
However, in the documentation the variable :scale is never set,
resulting in it defaulting to 1. The example script needs to start with:
\set scale 10
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com