The 20" barrel I bought went for about $115, mail order from Midway or a similar source. The cost of the shotgun was $199 at K-Mart about two years earlier. The barrel had rifle sights, and came with two screw in choke tubes: rifled and cylinder bore. It was Remington manufacture.
I've seen the Mossberg for quite a bit less, but I wanted the sights and the screw in choke. Now I tend to want the Vang Comp.
Of course, you could just check out gun shows, the internet, e-bay, etc., and find a cheap 870 barrel and cut it to length.
The Express uses cheap hardwood stocks instead of fine American walnut stocks, and I believe it is parkerized instead of a nice rich blue (it has a flat black appearance). My 20" replacement barrel is blued, but even so it doesn't look too bad on the Express . . .