AS others have said, I wouldn't pay more than $30 for the old MPC kit. Be careful on EBay though. There is also the the snap version which is smaller and horrible detail wise. Do not get any that say "Snap Tite" or "It's a Snap!"
http://images.productwiki.com/upload/images/mpc_star_wars_x_wing_fighter-400-400.jpg
There are many different releases of the original. Some under MPC, others under AMT/MPC/ERTL etc.. They are all the same model, however, later versions did not include a pilot figure (not that the pilot figure looked like an X-wing pilot anyway).
The earliest packaging looks like this.
http://www.scalemates.com/products/...ompany=mpc&name=luke skywalker x-wing fighter
These usually go for more money mostly due to the box art being in good condition rather than the contents of the box
Also I know for sure this release has the "pilot" figure
Ones with this packaging are usually cheaper. Not sure if they ditched the pilot in this release
http://www.scalemates.com/products/...?nr=8918&company=mpc/ertl&name=x-wing fighter
This is another repackage that you'll probably get cheaper than the one with the older box art
http://www.scalemates.com/products/...nr=38366&company=amt/ertl&name=x-wing fighter
Some versions have a flight display which is basically just a round piece of plastic you stick the model in so you can rotate all different angles.
http://www.starwarsmodels.com/images/boxes/xwingfd.jpg
Others have a "pro-plus" package which is just a set of useless paint pots added in and a crappy paint brush and a testors glue tube. This version has no pilot
http://www.scalemates.com/products/...?nr=8433&company=amt/ertl&name=x-wing fighter
Here's a great site that shows the time line of all the various repackaging of this model.
http://www.scalemates.com/products/product.php?id=335017