One recent example on the Android side (don't use iOS very often) was an app that regularly publishes curated watch faces for Android Wear. There are literally thousands of free, user generated ones out there and I can make my own without too much trouble but I liked quite a few of the ones on this app.

Additionally, they allow designers to submit their own watch faces and share the revenue which I thought was cool. It helps combat the glut of "brand" knockoffs that fill many of the free/user-generated sites.

Originally, they offered a "pro" version that gave you access to all current and future watch faces for a subscription fee. I was not very keen on this because, like so many, I tend to forget to cancel these things when I stop using them. I mentioned this in an app review and so did many others. We requested a one-time IAP for the "Pro" version and soon after, the developer did just this.

So I paid $10 and every week or so I check out the new watch faces available for download. I like that some of the money goes to the platform and some to the designers. I like that the designs are high quality and don't include any knockoffs or blatant copyright infringement. And I like that I could just buy the full app after trying out the free options.

I've done the same with similar light-verion/paid-upgrade apps but this was the first one I'd run across that offered both a subscription or a one-time purchase.