Last year I bought MLB.com's At Bat for something like $10 or $15. Then it was an "App". That meant, based on Apple's FairPlay DRM, I could install it on multiple devices as long as each device was synchronized to an iTunes instance that was associated with my App Store/iTunes ID (and credit card). In our home that can be up to five devices, though in practice only my son used it.
No consumer loves DRM, but FairPlay was well named. It struck a Jobsian balance between buyer and seller, like those .99 songs we used to have. It didn't get in my way very often.
It's too badFairPlay doesn't work that way any more. This year MLB.com At Bat 12 is just a shell for a $15 subscription -- and Apple's subscription/In-App purchase policies are an inelegant mess ...
... Non-replenishable In-App Purchases are items that only require you to purchase them once, and can be transferred to multiple devices authorized with the same iTunes Store account.
- Bonus game levels
- City guide maps
Replenishable In-App Purchases are items that have to be purchased every time and cannot be downloaded again for free.
Subscriptions are one-time services that must be purchased again once the subscription period expires.
- Extra health
- Extra experience points
- One-month subscriptions
- Location service subscriptions
Auto-Renewing Subscriptions are services that can be purchased with different renewing subscription durations.
- Weekly newspaper subscriptions
- Weekly magazine subscriptions...
... Subscriptions and replenishable In-App Purchase cannot be transferred or synced to another iOS device. Non-replenishable In-App Purchases and auto-renewing subscriptions can be transferred to another iOS device authorized with your iTunes Store account. For example, if you transfer a game from an iPhone to an iPod touch, only the game levels will sync over, the extra ammo and experience points will not be transferred...
Four different classes of In-App purchase, each with different policies on renewal, transfer, and multiple device use.
So which rule applies to MLB.com's At Bat 2012? Is it a non-replenishable In-App purchase that can be transferred between devices? Or is it Subscription that cannot be transferred? I couldn't tell from the description, but the answer is in a customer review  ...
... if you make the in-app purchase it is available on another device ... regardless of whether you make an in-app purchase or not banner ads are still displayed ...
So, for this year at least, the effective cost of MLB At Bat is still $15; it behaves like an In-App Purchase if you pay the $15 up front. On the other hand, I wonder how it behaves if you pay the subscription fee ...
FairPlay was a Jobs-class compromise. Apple's subscription plans are post-Jobs; I hope they'll take a second look at the mess.
 This is unrelated to my post, but I have to say it's rude behavior to show ads in a paid app. It's worse than rude really -- banner ads typically include clickable links that break Apple's feeble parental controls.