Your wish is my command.
It really depends on the brand and team (to a lesser degree) that you are talking about. Take the new Germany jersey as an example since my friend you are from Deutschland.
The new Adidas Adizero Germany 14/15 player issue home jersey that is sold in the stores is EXACTLY the same as the ones Die Nationalmannschaft players will be wearing in the upcoming WC (design, cut, fabric-wise, they are 100% the same), with one TINY MINI exception: The sizing system used. The Adizero Germany jerseys you buy in the stores are sized in the traditional S-XL way while the true match-issued ones used by the German players are sized using the 6-10 system. Other than this one little detail, there is literally no difference at all.
However, if we take our beloved Nike Barca jersey as an example, there is a bit more: The authentic Barca player jerseys you buy in the stores have one extra piece of fabric/cloth sewn onto the jersey, behind the back of your neck, cut in a half oval shape (
see here), with the DRI-FIT label, the size and "Made in Thailand" printed on it. This is not featured on the true Barca match-issued jerseys that our beloved Messi, Iniesta and others wear. For their match-issued jerseys, there is only one piece of fabric for the whole back panel, the size and "Made in Thailand" is printed on the same piece, therefore you don't see the extra arch seam you see
here. I am not sure if I made myself understood.
In addition, while the
wash tags (those tags sewn to the inside seam of the jersey showing the content of the fabric used, 100% polyester etc. and washing and ironing instructions) on the commercially available Barca player-issue jerseys are just like the ones on the replica jersey, the true Barca match-issued jerseys
have the abbrivated wash tag info printed on the inner side of the jersey itself so it eliminates the possibilities of the wash tags irritating the players in action. This is an unique Nike feature, as far as I know.
Again, hope this helps. Let me know if I need to clarify more.