Oliver Reichenstein, on Writer Pro’s pricing strategy (emphasis mine):

We experimented with different prices for iA Writer, and we debated all scenarios for Writer Pro, from free with in-app purchases to $200 for each app (iPad, iPhone, and Mac). We thought the ‘free plus in-app purchase’ way had the weakest chance. Competing with venture capital-backed Silicon Valley machine seems suicidal for an independent company. And the free-plus-in-app-purchase sends the wrong message for a premium writing app. Writer Pro is a tool for professionals. If you write, then $20 is nothing. Hold off if you’re just interested in testing cool new apps. If you want a better tool for your work as a writer, Writer Pro is for you.

To those shouting “But Pages is free! That other app costs 1 Dollar! And what about this feature comparison chart?!” all we have to say is: There are writing apps out there from $40 to $200 that have more features. But how many feel as good to write in? How many have the simplicity in workflow, Writer Pro’s syntax tools, or typographic excellence? Writer Pro leads and will continue to lead in innovation, and through it we’ll continue to strive for the best writing experience of any app.