It currently costs ~600g to level all your crafts enough to make ascended weapons. That’s as much as a precursor. But that’s not the worst part about it. It’s that if you take that path and make an ascended weapon, it does not progress you in the game — it doesn’t move you closer to a final state. Yes, it gives you better stats, but those stats don’t help you on your way to the next (supposedly final) item in the game, a legendary weapon.
In fact, the cost is so huge that going with ascended instead of directly to legendary will set you back by at least several months.
There is a trivial change that could rectify this: permit any ascended weapon of the appropriate type to be used as the precursor for that legendary or perhaps as the main ingredient in crafting a precursor. Voila! There’s now a true progression path from ascended to legendary instead of a giant detour.