You can't apply logic to crafting items from one system and expect that same logic to apply to a new system. EA used the ML gems for imbuing purposes solely because they already existed in game, and not because of their usefulness in ML recipes, or lack thereof.
Nor can you put a value on an item based on what it may or may not produce from what is essentially a non-related system. As I stated, people would much prefer to use their EC's for the ring, with the 50EP, which won't produce a fragment, rather than make weapons that may or may not produce relic frag.
And, despite your protestations to the contrary, relic fragments are an equal opportunity commodity. It's not difficult to make a legendary smith or tailor. I would argue that the tailor would be easier, as you can gather all your resources much more easily than you can smithing - it takes no effort, nor skill, to gather wool from sheep or cotton from fields. And you can take tailoring to legendary with nothing but cloth.
Smithing would require an extra stage, since you would have to also build a miner, but that's also not difficult - and with bods, the entire process would still, essentially, be free, with the potential to make a small profit in the end.
Is imbuing cheap to skill up? In the grand scheme of things, it depends on how you do it. Do you gather your own items, or do you buy gems from NPC's? If you gather your own, it's no more expensive than what you have to craft in order to imbue. And even then, one could argue that you can get skill ups simply by imbuing items looted from hunting. I know that's how I got the bulk of my early skill ups - unraveling looted items. It also provided more than enough resources to finish the push from 80 to 120, as well as the 120 power scroll.
Relic frags don't need to be cheaper for people to compete on an even playing field. They don't even need to be more common. As I stated earlier, they aren't even necessary for nice, and I daresay, top end, items.
I value items based on what they can create, not what happens when I have to destroy an item I have created. And what I value the most won't be what the next person will value - to me, White Pearls are probably of the greatest use, because as a PvM'er, it's in my best interest to be able to create the best single slayers that I can. To a PvP'er, Blue Diamonds, Fire Rubies or Turquoise may be more valuable, as they are used to maximize dex, str and int.
Simply put - the logic you are looking for doesn't exist, and the logic you are trying to apply would make Mr. Spock /facepalm...