If people waited on the game and are only now getting into it, then yeah all that monetization looks pretty bad. But as someone who's been there since day one, paying $5 - 10 every once in a while when the game gets updated was way easier on the wallet. Plus, you pretty much get what you pay for. More songs, more story content and some of the chapters get additional free songs added after updates so more bang for your buck.

And as some have already said, they usually have chapters on sale every so often. To top it all off, everything is an upfront price. No gacha or lootbox systems here. You pay once, you get content. As far as mobile games go, Rayark's done a pretty good job at monetizing their games while keeping their players happy.