Most carbines out there went thru "arsenal rebuilds", so most don't have matching parts. These guns in good+ condition, go for $550-700. Excellent condition will bring $800-$1000.
Also, you have to look out for the people that piece a Carbine together with parts they find. They'll try to claim that the gun is an arsenal rebuilt. These gun are worth $400-$500.
You'll have to pay $1000-$1500 for an "all correct" (as is came from the manufacturer) carbine in excellent condition. An all correct Winchester will go for more. "all correct" carbines are really hard to find since most were arsenal rebuilt and upgraded. I recently saw an all-correct 99% Winchester go for $2500.
Look out for Importer marks. These detract some from the value. Maybe 10-20%.
All the paratrooper carbines were made by Inland. An all-correct Paratrooper in excellent condition will bring $2500+.