The official stores are usually more expensive than the other stores. I remember when I was in milano the official San Siro store was 10 - 15 euros more expensive per shirt for both inter and milan shirts compared to the small football store behind the duomo. Difference was the san siro store had everything from both teams while the other stores couldn't match that.
I have four Barca shirts from the official Barca store when i was there. When i compare the shirts to the ones they sell for cheaper here, they dont compare.
So i would prefer to buy it from the Barca store with all the offical logos and everything. I can understand other stores like Kitbag selling it cheaper than the Barca store but what i dont understand is people or stores selling it hundreds of rands cheaper.