I throw a quid down the toilet? That's fine, I don't mind. I throw a fiver or a tenner? Woah dude, that's like, a Starbucks latte! Totally different (or not, but hey, that's what it feels like).
I wish Apple would start allowing time-limited trialware. The IAP machinery is already there, they just have to allow apps that stop working after 30 days if there is no payment. After 30 days, I have a pretty good idea whether an app is worth £1, £10, £50 or 0.