Unfortunately, as others have already mentioned, this is not as easy as "it's app developers who make the determination whether the cost is worth the benefit". Depending on your business, having an iOS app is not something you can choose.
Talking about my own experience, once we've made clear that In-App Purchase wasn't a fit for us as we already had our own payment system (we are a SaaS business), things got way more difficult to us. As you can imagine (but I didn't at the time), our app would be in review for weeks sometimes, we started to see arbitrary denials and a lot of "issues" not present on their guidelines started to be identified on our apps.
If there is one thing that I'm now sure is that, if you decide to not play their game (even though following their rules) there will be retaliation.
Talking about my own experience, once we've made clear that In-App Purchase wasn't a fit for us as we already had our own payment system (we are a SaaS business), things got way more difficult to us. As you can imagine (but I didn't at the time), our app would be in review for weeks sometimes, we started to see arbitrary denials and a lot of "issues" not present on their guidelines started to be identified on our apps.
If there is one thing that I'm now sure is that, if you decide to not play their game (even though following their rules) there will be retaliation.