I think it's understandable if it's purely aesthetic stuff, an item that doesn't affect gameplay drastically, or DLC-packs that don't impact the basegame. 

 The item thing happens too often when the developers either decide to make a weapon that could make going through the game an absolute breeze, or with AC:Black Flag's case were you could be entirely OP in multiplayer based off them alone. I wouldn't count GTA V's shark cards along the lines of this, as there are few things you can really buy (i.e tanks, but still easily attainable by those that don't get cards) that would increase your odds.

 By DLCs I mean things such as map packs or bonus missions that aren't exactly like an extension of the game, but more-so as if you were playing a side mission.