As a crafter I hate this idea. Who is going to pay lots of money for my double/triple melded wares when they can't sell it back on the wards when they find a better item? Prices will be determined based on how much gil people are willing to lose on an item rather than how much it is worth. This will force prices down, which will create a situation where items aren't worth making.
I certainly wouldn't pay 2 million gil for a double melded weapon when I can't sell it back for 1.5mil when I am done with it and I have to NPC it for 3000 gil. For that I would expect to pay no more than 500k.
Hopefully BoE items will not be the common crafted items but rather things like Dodore Doublet or other items that require a rare material or even drops from chests/dungeons that don't have the ex label.