For the veteran who needs 1350hp to add a slot, a tiny chance at an occasionall 250/1000 doesn't mean much.
The obvious solution is to cap the roster slot price, but every single Q&A has failed to acknowledge that as a possibility.
I think it's because it's pretty much how you monetize the 'in-between' players. Early in the play cycle, you get tricked into gambling on tokens. Late in the play cycle, you either regularly drop cash into the game to stay on top (the folks with character multiples, maxed covers the instant the character can be earned, etc.), or you change your play style to match your HP income.
In the middle, you have learned that token draws are lousy. You may still pull the lever, but you recognize the gamble. You keep a bunch of low-covered 3*s, because you never know when they are going to be required. You have to prioritize HP between buying covers, buying roster slots, and shields. If the cost of roster slots go up, eventually you cannot earn enough to juggle everything. So the developers gamble you'll occasionally pony up, you quit, or opt to play a little more casually.
I have put money into the game, but not in a long time. I can keep up with the roster slots with what I have/earn, and rarely use shields (and when I do, my nest egg shrinks fast).
But... what do I know? This is the same company that claims people buy 40 pack tokens because it's 'fun', so maybe I have the economics all wrong, and they fired the guy who knows how to change roster prices.