If you haven't played 80 Days, it's probably one of the most fun games I've played on my phone. I think I've seen maybe 20% of the total possible content after dozens of playthroughs.
I don't know what your financial situation is like, but $5 is a pretty low entry point, given all of the positive reviews (not even including mine). It's also low enough that it may not make sense to release a demo - it might be more work than it would bring in.
I've stopped worrying about spending $5 here and there, given that last year I wouldn't think twice about casually ordering a beer at a bar - especially when it comes to paying for software.
The average salary in my country is $30/day, but it's not so much about that as about the fact that it's very unlikely that I'll like a game, so at $5 per game the expected ROI is negative. I'd like something that can raise the certainty before I purchase (e.g. a demo, or at least an extended trial period).
Too bad Google only allows you to try an app for 15 minutes or so now.
As an aside, the Sorcery games referred to here are very faithful adaptions of Steve Jackson's Sorcery! adventure gamebooks, the pinnacle of the Fighting Fantasy series and total catnip for the eight-year-old version of me. Buying and playing them has been a huge nostalgia trip.
Not very comparable, except that they both produce some form of text interface.
Ink is most similar to ChoiceScript [0], which powers Choice of Games's Games. Twine [1] has the same structure but is a visual editor, not a scripting language. Undum [2] produces the same kind of system, but is Javascript rather than its own syntax. Dendry [3] powered Varytale's games, but the open source version seems abandoned. For completeness, though a webapp not a language, StoryNexus [4] is a hosted platform with a database-like interface (fill in a bunch of forms), it powers Failbetter's Games.
Inform7 is very impressive as a natural language syntax. But the kinds of 'parser' based games it is best suited for have always been rather niche, because they require a certain familiarity with the form.
Hey, Joe here from inkle! Sago's reply is really good, but broadly for those two specific languages: Ink is designed to be one component in a larger game engine - the runtime has a simple core loop of choice -> text generation -> choice. How you implement the UI is up to you (right now we have a C# runtime designed for usage in Unity). By comparison, Inform7 is designed for building standalone parser-based text adventures in the vein of Zork and its more modern successors.
Well, the biggest difference is that Inform is by default built in a way that describes a world, while Ink is built in a way that describes the flow of a narrative.
It's like the difference between Inform and Twine.