First off, I'll let you know this is the wrong section, and to use the 'what's it worth thread' here
next time, no worries though.
The answer to your question depends on a few things: if it is a Phenom or the original X7, the condition it is in, and what extras you include with it (electro grip vs mechanical especially).
Clean, mechanical, and functional original X7s can go for up to $130 or so with no extras.
Clean, mechanical, and functional Phenom X7s can go up to $200 or so with no extras.
Hope that this helps!