While on the one hand I understand the problem with the "race to the bottom", on the other hand, it can still end up having tremendous payoff. Look at Angry Birds (or insert any number of other success stories). 99 cents for the app, but look how many millions of copies it sold, because it was cheap, which lowered the barrier to entry, and it was well-made, so users were delighted with the purchase (and at how great a value it was!) and were only too happy to recommend it to others, to buy it sight-unseen based on the enthusiastic recommendations of others, to buy additional copies of the game for their iPads/Macs/Android, etc.
It's like that age-old lemonade stand game. Price it too high and you make a lot of money on individual sales but you get fewer individual sales. Price it too low and everyone wants it, but you don't make enough money to sustain it.
I'd say that 99 cents is a decent "try it and hey, if you don't like it, it was cheap" price for an iOS app.
Mac App pricing may be different, though, depending on whether or not a "free trial" version is available (through the App Store, or elsewhere). If I can't try it out first to see if I actually plan to keep it, then I wouldn't risk paying more than maybe $5-10. If a free trial is available so I can make sure I like the app before buying it, then the sky's the limit.