This got me thinking about something.

What's to stop an unscrupulous developer selling an app for, say, $1.99 with the (implied) promise that the app will work forever and then, once people have bought it, turning off the backend so it no longer works?

Is this illegal? Would Apple shut down the developer's account?

It's not illegal, and Apple wouldn't shut down the account.

Many companies do this with games that have a strong online component.

I think it would depend on the jurisdiction, and the "degree" of "implied promise". Eg. in Norway there's pretty strong protection for (private) buyers. On the other hand, proving fraud in the case of the company behind the app simply declaring bankruptcy/shutting down would probably be pretty difficult.

I suppose a relevant study would be Microsoft Zune/music store, and/or Yahoo(?) Music that shut down and killed the DRM servers, effectively removing music people had "bought"?

I'm not sure why Zune keeps coming up as an example in these threads. It got rebranded to Xbox Music, but all the servers are still up and anyone who subscribed still has all their music.

An earlier Microsoft DRM that was used by a bunch of services (PlaysForSure) was indeed shut down, but it's not the same thing as Zune.

Oh, I was thinking of the earlier one. I suppose it's often conflated with Zune, because of the spectacular flop of the Zune devices/rebranding thing.

Seemingly, a compromise is required, since "$1.99 for unlimited use, forever" is unsustainable if there are on-going costs.

I think there's a middle ground to be had though. For example, if the average user sends 1 article per day, offer 400 articles for $1.99, and in theory you have a recurring billing model that also doesn't require too much worrying from the user's point of view.

The other model might be $1.99 for unlimited use, and then release V2 of the app with new UI/features, and do an annual release model. It works for many apps, eg developer tools like IntelliJ. Would be interested to know if it works on app stores without getting grumpy user feedback though.

This is a really good point.

However, there are some apps that do have a model of $xx for unlimited use, even where there are ongoing costs.

This is sustainable if the app continues to gain new users, hopefully at an accelerating rate. It works like a pyramid scheme where the new users coming onboard subsidise the cost of the existing users.

Usually they release V3 and discontinue support for version 2. Maybe version 2 is somewhat useful still, but it probably doesn't have support for what you need anymore.

maybe the ploy should be to get to V3 as quickly as possible as this pyramid / growth rate collapses or cut costs in V2 (cheaper servers, more efficient code - if possible). This is an interesting thought to me nonetheless.

Absolutely. If you force the user to choose to pay on an item-by-item basis, they're definitely going to use it less.

For me, it's a bit like mobile phone data charges. When I used to pay per mb, I hesitated to use cellular data at all, but now I have a (high) monthly allowance, I now use my phone a lot more, even though the cost is higher.

Perhaps the developer should try switching to a pay-monthly kind of subscription, at least then the users aren't having to make that 'is it worth it?' decision each time they want to use the app.