I think the price of the cab figures is $4.00 each but I'll check the Lionel site.
Also, if you install an LED for the headlight you might need to add some additional ones to light up the interior. Since I used a 10volt incandescent bulb it not only lights up the headlight and marker lights but also the cab interior.
I got those prices off the Lionel site.
I install LED's all around, I feel they look much better than the incandescent bulb for headlights. I also mask off the headlight totally, the cab lights will be separately controlled. I have a module I install that turns the cab lights off as the locomotive starts moving, the same module turns the headlight bright for Rule 17 lighting. I might even make the cab lights directional, haven't thought about that yet. 
