So part of the issue is that this is also the currency for catching up with essences and corruptions. So if I were to try to spin up a new Hunter to be reasonable to take to heroic raid, I might be looking at wanting 70k+ echoes (and hunter uses cheap corruptions). And some of that will be reduced by running visions, and getting lucky on loot drops. But assuming you are doing a 15-keystone, major & minor assaults, 1 vision, all the daily emissary quests, you are getting about 5k per week. You are still looking at 2-3 months to spin up a new character.
I mean, they could have done something where the cost varies with cloak level. So if you are getting your first upgrade, it costs 5, but if you are buying the one that caps your cloak it cost 2500, with scaling in between. So you could probably get a bunch of levels, but would need to do a bunch of content too.
I guess the real question is, how much do they want you to be able to catch up? And I think the awkward bit here is you have possibly 3 different directions you need to be catching up: essences, corruptions, cloak levels. And they are all sharing the same catch up currency.