I really hear you on that, but yea sadly what you have an issue with happens in any and all games.

Business realize that there are people who are more than willing to be impatient and spend now, and * up the new biggest thing, then later on... much later on they will add the thing you spend 5000$ on in the shop for 100$, this is an attempt to keep free players happy and player, aka a way for them to keep 'content' for the whales. Without this, more free players would get up an leave, but sadly that can often come at a snails pace, which is why games tend to fade away from spotlights/the height of their popularity.

It is nothing short of a painful chore trying to keep up/wait for them to release a cheaper way to get certain ninjas/stuff for power, sometimes they don't even do it, it is entirely up to them, if you/others like you could be more patient/speak with your wallet you could reclaim the 'power' so to speak, eventually they will wise up and see that the more people that can afford something... that is better for them. A thousand people spending $50 on a ninja/item for power, is far better than a few spending $1000 on a ninja. They will have to wise up to that fact/see it as the undeniable truth or they will fail, and have no money to run their business, but sadly we all tend to fall for that practice in one way or another. (Take the cave keys for example... I spent all of mine as soon as possible, but later they release a event where the more you spend in there, you get some more in return, which allows you to get a bit higher, when you do it. I even do this with the seal scrolls, I spend all of mine right away, really rather dislike waiting for 10 and getting nothing. xd lol)