Apple Prevents Omni Group From Offering Discounted Mac App Store Upgrades

Last week, The Omni Group released a program called OmniKeyMaster that would allow users who purchased older Mac App Store versions of the company's software to purchase discounted upgrades in the future, directly from the company.
Today, the company said it would be unable to offer upgrades to Mac App Store customers because of Apple's App Store policies.

My apologies: I’m afraid we will not be able to offer upgrade pricing to our Mac App Store customers after all. So long as we continue to sell our apps through the Mac App Store, we are not allowed to distribute updates through other channels to apps which were purchased from the App Store.
We still feel upgrade pricing is important for customers purchasing serious productivity software, since the initial value received from purchasing an app like OmniGraffle or OmniPlan is much different from the incremental value of upgrading that app from version 5.0 to version 6.0. We will continue to ask Apple to support upgrade pricing in the App Store, and I would encourage others to do the same—but until that happens, upgrade pricing will only be available to customers who buy our apps direct from our online store.

A number of developers have asked Apple for the ability to offer upgrade pricing to purchasers -- a very common software pricing strategy -- but the App Store requires that upgrades either be offered for free to existing owners, or sold as a completely separate offering on the App Store, at the same price for all customers, new and old.

Red Sweater Software's Daniel Jalkut called the move a "chilling message from Apple" and filed a bug report with Apple requesting upgrade pricing support for the App Store:

The impact of Apple's continued lack of support for upgrade pricing has been increased by an apparent effort on Apple's part to enforce 3rd party developers trying to accommodate upgrade pricing through their own means:
http://www.omnigroup.com/blog/entry/update-no-upgrade-pricing-for-mac-app-store-purchases
Most of us Mac developers are loyal Apple fans who would like to support the Mac App Store and keep our customers who purchased on the Mac App Store within that system. By not supporting an upgrade mechanism for these customers Apple leaves us in a position where we're forced to either treat Mac App Store customers as 2nd class customers or to forego across the board the expected compensation for major upgrades to our applications.

Apple has moved away from upgrade pricing in recent years, choosing instead to slash the prices of its major software titles instead of offering discounts for current owners. Final Cut Pro X, for example, costs $299 while its prior version was $999.