The RC8 is a new program. To make an upgrade possible IPACS created a "bundle" for RC7 and RC8 for $99
Only RC7 users can purchase this bundle
If you see the full price on this page
https://itunes.apple.com/de/app-bund...59842259?mt=12
there can be different reasons
- you are not logged in into your iTunes Account
- you changed your Apple ID or are using new one compared to the one used in the original RC7 purchase
If you are logged in you should see the reduced price
After purchasing you should get a full RC8 download without deleting or rebuilding the former RC7