I only have one HWK, Firespray, and rebel Y-wing. I was thinking about buying a second Most Wanted just for the cards and ships. I want to split it with my friend and give him all the pilots and bits for the three retrofits, along with cards I wouldn't need a 2nd/4th of (e.g. the duplicate uniques and astromechs) and probably an autoblaster turret.

How much do you think that would that be worth if we are paying full price at an LGS?

Well...

Depending on your Point of View, those extra cards, dials, ect... are free. In that the retail cost of 3 ships is $45, and you're paying $40 for the MW box.

That said, if I'd ask for $10-15 at the most for the extra stuff.

In all honesty, at $40 you are getting three ships that would cost you $45 individually. Anything you got above that would be a bonus, IMHO