New information has emerged in the 20 odd years since I first posted this...
First it turns out that you can keep doubling the amount spent on gin by
bumping up -- note, not a complete list -- to Tanqueray or Bombay,
then Hendricks, and then The Botanist. YMMV.
Also there are some
other choices for vermouth, including Via Extra Dry, at similar doubling
price points. However, I have found no better olive than Santa Barbara.
PLUS, there is an ASA standard to consider:
Safety Code and Requirements for Dry Martinis
AND we all know that
Safety is Job Number One