It's not purely about money making, a lot of silent playerbase (including myself) thinks that 4 star rule is very good balance added to those ninjas compared to china.

Ninjas with skilltrials are clearly way more powerful than basic 3 stars on release so its fair for them to be expensive to what power they bring. I'm really hyped about GNW Madara trials and don't see why he should be 3 star when he counters half of the current and future metas.

4 star rule for ultra rare and treasure ninjas is another story tho ... (I agree getting 4 star hashirama or 10tails madara is total bs)