Adobe has not announced the policy yet, but my guess is that they will allow you to use a previous PC purchase toward upgrading to the Mac version. I doubt, however, that “low cost” will be the right word for it.
Adobe does not care how many parts of the bundle you already own. If you own Photoshop you get the same break as someone who has Photoshop, After Effects Standard and Flash.
In fact, if you had every product that made up a bundle, you still could not get an upgrade to the bundle for the same price as someone with the actual bundle. And the bundle must be purchased in order to get at least one of the cool features (Dynamic Link).
Poor marketing if you ask me.
Steven
https://www.stevengotz.com