Why can't it cost 1 coin?

It needs to be 75,000,000 coins because:
If the Rare is 1 star, buying it will be a breeze but activating it would be a challenge because you need to get all rare monsters in the island it is in
The Epic is 1 diamond, the same like Rare but it would be even harder because you need epic monsters
For Wubbox, the reason why it costs so much is because it would be kind of easy to box all monsters required to activate Wubbox so the players need a challenge for each Wubbox kind so if the challenge for Rare is to get rare monsters but in return, costs 1 star and if Epic Wubbox's challenge is to get epic monsters but in return, costs 1 diamond, the Wubbox's challenge is the worst. You guessed it, grind coins.
Call me a nerd all yall want, it's basically just logic