The moral of the story being, ditch the money grabbing bar stewards at Apple!
Not really. The moral is: buy DRM-free from the original source, wherever possible. As Mr Web Droid notes, any 2000 AD content can be accessed on other devices – in other words, you can buy in 2000 AD's shop and access said Progs in the 2000 AD app, as long as you use the same Rebellion ID. And you may as well buy everything direct from 2000 AD's shop, so someone else doesn't get a cut.
Also, if you're using an iPad, strongly consider grabbing
Chunky, which is a superb reader for 2000 AD and beyond.
(For anyone not in the know, what happened with content pricing in the App Store is that sterling's crash led to Apple rebalancing prices. Unlike on Google Play, the iTunes Store has strict worldwide 'tiers', which mean apps/content priced at, say, £2.99 will be $2.99 in the US and $4.49 in Australia. On Google Play, you can do this kind of automation, but can also override it. Although this also means if/when 2000 AD drops its pricing to the next tier down – £1.99, the price will also drop everywhere else in the world, too, so the US price would be $1.99 rather than $2.99. Not fun from a business perspective, but there you go. Apple could offer more flexibility here, but the pound tanking is what caused all this.)