The audience on the Mac App Store is not yet large enough to sustain low prices (like the iPhone can, sometimes) – it’s just not feasible. If companies keep selling software at bargain basement prices without a large enough market, it doesn’t end well – they go out of business and if that happens, the very people who love great apps lose too.
Realmac has gone through some changes for the pricing of Clear for iOS. On the Mac, they’re returning to pre-App Store days with higher prices and no discounts.