The Omni Group, makers of popular productivity apps like OmniFocus, OmniGraffle, OmniOutliner and OmniPlan have released a small, free OS X app that allows users who have previously purchased versions of its software through the Mac App Store to qualify for upgrade purchasing through the company's web store for the next version of its apps.
Called OmniKeyMaster, the app works by searching your hard drive for Omni apps from the Mac App Store. It then lets you purchase the newest version of the app at upgrade pricing. As Omni Group explains on their website:
OmniKeyMaster is a clever way to get around the fact that the Mac App Store doesn't offer upgrade pricing -- something Apple will hopefully change in the future.
OmniKeyMaster is a simple app that finds App Store copies of Omni apps installed on your Mac, then generates equivalent licenses from our store -- for free. This gives Mac App Store customers access to discounted pricing when upgrading from the Standard edition to Professional, or when upgrading from one major version to the next. Another benefit: since they don't have to wait in an approval queue, our direct releases sometimes get earlier access to new features and bug fixes. OmniKeyMaster lets App Store customers access those builds, as well.