The winer is RickMD, could not have said it better.
Remember the Remington 700 ADL? It was the exact same weapon as the CDL or BDL except it had an inexpensive synthetic stock and no floor plate. Same rifle but without the beautiful stocks on the CDL and BDL. The only reason the ADL went away is other manufactures were cutting into Remington's market share and they needed a cheaper version to complete at the lower end. The came a series of 710 7 this and that and who knows what is next. But those are not 700's. The entry level 700 is now the 700SPS and it is every bit as good as any 700.
So much of this is "Marketing". For Example: The Remington Special Purpose is simply the same applied matte finish as the Express but the metal is polished more before the application. I learned this by asking why the same barrel labled Special Purpose was $40 more then the exact same barrel labeled Express. Man that is a lot of polishing. If you look real close at both barrels you can even tell the Speical Purpose finish appears smoother. Like that matters. Here is a case of a buyer thinking he is getting a better finish when it is still the same Express finish.
Much of the pricing at Remington would drive you up wall if you did not know why. For example: The 18.5" Matte finish bead sight Express barrel retails from Remington for $131 and this is the barrel that comes on the Express HD 4+1 and used to come on the 6+1. Yet, the 18.5" Parkerized bead sight barrel that comes standard on the 870 Police retails from Remington for $101. Yep, the Express barrel cost $30 more then the Police barrel.
Now I am having fun. That 18.5" Parkerized Police that cost $101, get that in 20" Parkerized bead sight and it is $150. However, the 18.5" Bead sight blued Wingmaster barrel is $150 and if you get that barrel in 20" it is $117. Anyone confused yet? And yes, these type of difference occur all through the Remington parts list as I purchase over 60K in parts alone each year with a high of over $80K in 2009 thanks to O'boma so I know the parts list very well.
Now for the answer. It is a combination of Marketing and units manufactured. At least that was the answer I go when I was at Ilion. So with the facts above sinking in to some of you who can't accept the Express, the Police and Wingmaster as the same weapon I invite you to look over the Remington parts list. For Example: Stipped Parkerized Police receiver $247. Stripped Express receiver $247. Stipped Wingmaster receiver $247. Express breech bolt $97, Police Breech bolt $97, Chrome Wingmaster breech bolt $97. and of course there are only two forend tube assemblies made, one for the Super Mag and one for all other 870's and there is a $5 difference in the trigger plate assemblies between the Police and Express as one if polmer and one cast aluminum but all the parts are the same, every freaking one but a little black spring, but the Wingmaster cast aluminum trigger plate is $84 same as the Express. If you built a 4+1 police and 4+1 Express with the bead sight barrels and with the exact same stocks the 4+1 Express would cost you $26 more to build the 4+1 Police. See any Marketing here?
I found 2 small burrs that I was able to remove with a light file and sand paper. These 2 small burrs might have been caught in a police build maybe not. They might have affected the way the gun performed maybe not. One burr was on the bolt. I guess I am just obsessive but man that express eats everything I feed it.
