I've just posted a message about how the slayer weapon should be considered.
I'm not going to repeat but in short if its considered as a magic property, it has nothing to do inside a "standard" crafting menu.
If in contrary a slayer is human made, it has to be in a crafting menu, otherwise what it means ? It means that our crafters characters are totally nuts, they don't know what they are doing, and they are very surprised about the result of their crafting.

See what I mean ?
Now about the market's going down etc, this is not true.
I'm not asking for a better probability to craft a slayer.
Let's say today you need to craft 100 bows at brit craft zone to get a Repond, with the Slayer crafting menu you will also need to craft 100 bows to get 1 Repond. Same probability. No change on the actual rate you get your slayers.
No difference.
But what could be different for example, you would only loose material when attempting to craft a slayer, not having to craft hundreds and hundreds and hundreds of normal bows or swords that you just throw in the trash barrel or recycle
You would loose some logs or iron but you only craft the kind of slayer you need, except that you will never be able to chooe a Super Slayer or a Lesser Slayer, so it keep some spice and some random in the art of making slayers.