Genuine items are items obtained by purchasing a game with promo items within the promo period. This was done so that after the game is out, the items will be put into the normal drop/craft system, and you can tell the difference of the ones obtained by buying the game, and the ones that were crafted.
Promo items that were crafted (Such as the Three Rune Blade) will have Yellow Text instead. For many items, Genuine doesn't go for much more then the normal version, due to actually being the more common version (Though I think people are starting to adopt the "Vintage" mentality with them, that they are "limited")
Also to note, while the Three Rune Blade can be crafted, it is a generic craft, and has right now a 1/8 chance of getting it. And the generic craft isn't cheap, it requires 8 weapons crafted into a scout token, melee token, and scrap metal. As such, to almost a 50% chance of getting the Three Rune Blade, you would have to do 5 generic crafts, costing 40 weapons.