I'd need to see the purchase page to fully form an opinion on this. Apple has rather strict guidelines for displaying cost and that appears to be one of the most important parts of app review. I'd equate someone being surprised by a subscription cost to someone not looking at menu prices when eating out: all purchases through the app store use the same sheet to display price, renewal period, free trial, etc when requesting payment.
Of course, the app's premise is a scam, but my comment was about the ease of canceling and managing subscriptions. Dare I say that apps like this would be even more bold and prevalent if alternative app stores were available.
There are also scams costing people money without using iOS, for example where the person is tricked into thinking they have a debt and sending thousands of dollars in cash to a random address[1]. What’s your point?
And yet there are scams that are costing users $5 million a year, or more, on the iOS App Store[1].
[1] https://news.ycombinator.com/item?id=26794228