You also don’t know how cube upgrades work. It takes the base level requirements and adds 5 for exceptional and adds 7 for Elite. The upgrade will require level 28 not 23.
The Angelic Sickle is the worst set weapon despite it having ED… 
Here is proof:
- Base Weapon Speed is -10
- Base Damage is 3-8 (5.5 Average)
- with 2 pieces of set it goes to 5-14 damage(9.5 Average)
Lets compare to Cleglaw’s Tooth which has the same base weapon speed:
- Base Weapon Speed is -10
- Base Damage is 3-19 (11 Average)
- 2 piece adds 1.25 max damage per level. At level 12 it would add 15 max damage bringing the weapon damage to 3-34 (18.5 Average)
As you can clearly see, a white Long Sword is already superior to an Angelic Sickle with 2 set piece bonus.
Please stop fixating on just ED. There are other things to consider as well when considering weapons. High ED means nothing when the base damage is crap. A white Long Sword already has a 100% higher base damage than the Sabre. Even as Exceptional, a Shamshir has 10-24 (17 Average) base damage compared to the Rune Sword with 10-42 (26 average) base damage. The average base damage of the Rune Sword is already 52.9% higher than the Shamshir.
Again, Steel in a 2 socket weapon is far superior at level 13 than Angelic Sickle with 2 piece bonus.
Lastly, what’s cheap about this recipe at level 28?
1 Ral Rune + 1 Sol Rune + 1 Perfect Emerald + Normal Set Weapon = Exceptional Version of Set Weapon
You can use those runes for sometimes much better.