This is how it's been since software first existed. Shareware.
When the Internet came along it was free software with a Buy Now button that took you to the website where you would purchase the full version or a license key.
I thought this was the "norm" for selling software, and it always has been.
Barring a shareware style demo, I rarely make a leap of faith into a new software product. However, stellar reviews and/or at least a video example can make up for that. Maybe one exception would be updates to products I currently use.
I too have found myself watching videos of apps (particluarly games) before buying now if they don't have a free version.
I was actually considering doing an experiment where I removed some of my free versions of apps from the Market and put in better videos to see if I could get the same results.... I doubt it, but...
TL; DR: "study found that in-app purchases [...] accounted for an astonishing 72 percent of Apple iphone app store revenue in July, up from 28 percent just a year ago. "
When the Internet came along it was free software with a Buy Now button that took you to the website where you would purchase the full version or a license key.
I thought this was the "norm" for selling software, and it always has been.
Free to try, then you must buy.