Just upgraded to Mountain Lion and I have to buy iPhoto again?
You can always re-run the disc based installer and avoid re-purchaing the app from the App Store. Eventually you will buy a new Mac which will then allow you to claim the App Store licenses for iLife without paying additional fees.

I'm stuck in the same boat with Aperture. The convenience of the App Store isn't enough to make me want to re-pay for the software I have a DVD based install.