Just FYI - you're going to spend far, FAR more time and effort reading release notes and manually upgrading containers than you will letting them run :latest and auto-update and fixing the occasional thing when it breaks. Like, it's not even remotely close.
Pinning major versions for certain containers that need specific versions makes sense, or containers that regularly have breaking changes that require you to take steps to upgrade, or absolute mission-critical services that can't handle a little downtime with a failed update a couple times a decade, but for everything else it's a waste of time.
If they can charge 30% less without Apple's fees, then why are their prices the same whether you buy on their iOS app or direct on their website? Why have they been overcharging users who don't buy through the iOS app by 30% all this time?