Neither of the price guides I own cover Westones. My hunch is most of them sell for between $200-$400 depending on the particular model and condition.
In addition to fishing for information here, you might try a post over at the Westone Forum. Those fellas seem to be pretty serious about their Westones and might be able to give you a more precise estimate of the value of your instrument. 
You can find the Forum here:
Statistics: Posted by VintAxe — Fri May 09, 2008 8:33 am
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