This is where it gets complicated...
To release an Android app would cost £25, as a one-off fee to set up a developer account. You can develop on Windows, Mac or Linux - A £100 PC would do the job.
To release an iOS app would mean £79 a year as a developer, plus the development tools only work on a Mac. And some stuff only works on a real Mac, so you'd need one of those. Take the cheapest Mac Mini and spec it with 8GB of RAM to make it usable and you've just spent another £569. Let's assume that's got a five-year life span, so total cost over the five years of £964 (plus a bit for the developer cost going up).
Apple take a 40% cut, so realistically the iOS app would need to sell £350 a year just to cover costs...
And they wonder why they're losing market share.