So lets see. Grinding arena starting from t2 nets you an avg of 5800c / 50 energy.
5* weapon in shops = ~100k
5* weapon crafted: 300e + 200e + 100e + 50e + 16kc + 6kc + 1kc + 2kc +4kc = ~104kc
This is excluding the fact that you also have to collect materials, as well as level the equips to at least lv5 to go from 3*->4* and at least lv10 to go from 4*->5*. You also have to get your hands on the recipes somehow.
Aside from the fact that you can spam 2* items in hope of getting an unique to upgrade. (costs ??? energy because each 2* crafting attempt already costs 50e) Most of the 5* weapons (except for the drop only) may randomly appear in the shop in town.
Well normally the energy prices are half what it is now. With how they are now, mist has gotten more valuable than ever. You also have to remember vendors very rarely sell 5* gear. I've only ever seen a Radiant Sunshard ever being sold actually. There's a lot of gear I've never seen in the vendors like angel set or gunslinger set, etc (Most weapons are in the shops tho). Crafting is usually cheaper but there's some inflation in the energy prices now ~_~