I feel like a big part of the problem is that the entire space is filled with junky 'free' apps, and getting to something high-quality is difficult. And so we're trained not to value apps because they're awful, and therefore not worth paying for anyway. A vicious cycle.
If the apps are reasonable quality and solve a problem, what's $5 or even $10? Many people spend around that for a cup of coffee that will be gone in 30min. I'd happily pay that for a good app - if only I could find one.
I'd LOVE to see super-cheap subscriptions too - like maybe ten cents or even less per month. This solves another issue: Once a dev has gotten most of the one-off sales they can, there's not much incentive to maintain the app. A subscription model is much better for this, but for most simple utility apps it needs to be very cheap.