I came across this podcast featuring an interview with Richard Sexton of CarolinaRustica.com as he discusses his company's growth from a startup bricks & mortar "upmarket" furniture retailer to a $4M /year online retailer, primarily through successful search engine marketing. His annual PPC budget is $350k (8-10% of his online sales).
It's quite informative.
The podcast is as at http://www.scottfox.com/2008/09/ppc-keyword-ads.html