Job Key..
Is the most important item and can be exchanged to Relic -the required materials to promote your heroes to the higher rarity..
It has very high demand because new hero is released once every 3 weeks..
And you need a lot to Limit Break, MTT and to make an Insignia..
Player without Prestige bonus with Player Level above 100 can generate 10 Job Key daily (I'm level 106)
Another Job Key source is from Expedition and Guild Quest which can give you 2 and 1 keys..
3 relics can be produced in Academy buildings every day..
And of course you can buy Job Key from Store for 25 gems / 5 Keys (the price multiplied after purchase)
If you lucky you can also get the Job Key from either Marketplace, Wishing Well, Royal Chest, Arena Chest and Job Key Quest from Legendary Story Maps..
Event Bazaar or some floor at Tower Events also can give you a Job Key..
If we count everything excluding the luck and Event, we can gain 18 Job Keys and 3 Relics including the one from Store -per day..
A hero need 70 Relics -means we can promote our Hero to 5* every 3.34 days
Or equal to...
3 Hero / 10 Days (250 worth of gems!)
2 Cycle of Event is 6 weeks (42 Days)
2 or more hero is released during this period..
42 days worth of 882 Relics (cost you 1050 gems!)
In 42 days you can promote 12.6 unit, let's round it up to 13..
That's sound a lot..
But remember..
In 42 days (which is not a short amount of time) two hero has released..
In that period of time, you may or may not need unit to MLB, make an Insignia, trying new unit or even creating new squad..
MLB (6 unit) a one single Hero is equal to 420 Relics..
While completing Insignia (3 unit) need 210 Relics..
So in 42 days you can MLB two unit and make half of insignia..
Or make an 2 Insignia and lvl 38 Hero..
Although I understand that they're just trying to sell Job Key bundle or any bundles with JK included..
I have came up with this suggestion..
They can adjust the final numbers and can consider one of the best option (according to them)
~ Increase the JK cap (2-5 more depending on Player Level)
~ Reduce the Relics needed to promote Hero to 5* (up to 30)
~ Increase the amount of Job Key sold in Store (10 JK / 30 gems)
~ Increase the amount of JK rewards in Wishing Well (5-10)
~ Increase the amount of JK sold in Marketplace
~ Increase the Academy cap
~ Increase the amount of JK gained via Expedition (5)
~ Increase the Guild Quest rewards upon completing Killing Quest (5)
~ Sell JK in Arena Merchant (50 JK / 500 BT ~ 1 week cool down)
~ Include JK as a reward in Raid Chest
~ Relics Dungeon as a Daily Event (similar to Talent Dungeon)
~ Relics or JK drop in Story Maps / Event Maps etc..
~ JK rewards upon promoting a Hero to certain rairity
~ JK rewards in Daily Quest