I've been thinking the same thing for a while. The simplest argument in favour would be that people would immediately be much more careful in their selection. If I have to fork out money, I'm definitely not going to pick the buggy / low quality / app with dodgy permissions to the system, uses my location andor other data for ads revenue /etc. It means those apps wont have an audience and die off, because there's no incentive. And we'll all be better off...Not?

I'm so sick of all the crap that is out there, I wish I can just pay a fair amount and get an app that gets close to what I need, is of quality and without hidden agendas and issues.

Free is a funny thing, people's behaviour and expectations go out of whack. Even $0.99 is better than free. It's often better than $9.99 also. Free makes that people expect everything to be free, even quality software.

Quality software is hard to create. You cannot hold it to a developer if he gave it to you for free; he has no reason to really make it good...If you haven't actually put out software at a price, then you don't have first-hand experience of the responsibility it puts on you. The responsibility we need to create a better (app) world.

And if you want to throw the open-source argument, just remember free and open-source is not the same thing. If you're confused go read The Free Software Definition: http://www.gnu.org/philosophy/free-sw.html

I agree with previous comments, there should be atleast a trial period, I need to be able to figure out if this app will meet my needs.