Will the Paid Authentication Event be Profitable?

I was hesitant to make my first post after getting Frontier, but with the Paid Authentication event, I wanted to check if it's profitable. 100 coins + 30,000 gems is effectively 400 coins. So, if it's 80 yen, considering Google Play Points, it's barely profitable. But what's the cheapest price on this app?? That's what I mean. There's also a check-in event and a hidden quest, but...