I'm up for every suggestion that lowers the cost of upped pillars!
1500
=1 quanta in game, isn't a big deal
And by The Almighty Zanzarino,while a tower isn't so much more useful than a pillar, an elite Gost of the past is so much more better than the unupped .I often have the feeling that a pillar is a downgraded tower...
More quests would be awesome.A 'must' quest would be 'upgrade your first card!you will recieve 1500
!'(way best and more encouraging than actual 'grind 1500 to up a card so you will have someting to spend on')
I wouldn't also dislike events like 'today upgrades cost 1399
!' as soon they last at least 24h.
About pillars:
1)upping pillars should cost between 500 and 1000
2)upped pillars are more worthy(side effects like gain 1hp or such)
or they provide more than +1 quanta on entry
or they have a chance to produce more than 1 quanta each per turn
3)upgrade in block:1500 coins and you choose 2-3 pillars to upgrade