Rally cars Are titled, registered, and street legal or they are not allowed to compete!
Prescott and Idaho have over 200 miles of Transit on highway, and city roads. quite zones too, penalties for noise violations, etc.
Are you including suspension, brakes, wheels and tires for 5K?

If so i apologize that's an AWESOME DEAL assuming if so, how much with out that stuff?
you have $1,000 head lights

, ... are they HID Xenon headlights? that would be sick for a rally car (you'de still need supplemental driving lights)
if by shell you mean only the chassis, doors, brake lights, complete with some sorta head light, corner lights, turn signals, a horn, stock a-arms & rear track arms, stock subframe pieces,
no motor, no tranny, no rear diff or drive train, no suspension, no wheels no tires, no seats, no belts, no fire surpression, no first aid kit, no triangles, then ya i still think 5K is a bit high.
http://www.specialstage.com/classifi...ct/1861/cat/13 stripped and acid dipped 1900 obo no cage but that's really just 3k away and you'de have new seats and belts
http://www.specialstage.com/classifi...ct/1803/cat/13
8K fully build, motor, trans, seats, belts, spares, tires ...
http://www.specialstage.com/classifi...ct/1824/cat/13
$5,000 for a fairly fast Group 5 car, fully built ready to go (its not a GD Shell but hey honestly he's beaten a lot of stock wrx's with it)
rolling caged shell (Ford focus)
http://www.specialstage.com/classifi...ct/1816/cat/13
base model price of a focus is 2K lower, but he's including the motor suspension, brakes
So in conclusion, no i don't think 3-4K is Crazy talk for a caged, FIA or rally log booked shell. but again maybe you were including more than i was expecting from the word "shell"