If I purchased a feature, will I pay for it again?
The answer is: No.
You will be able to download your purchase again for free. You purchase the feature once.
If you lose your In-App Purchases because your app was accidentally deleted or you had to restore your device without a backup, or you got it on iPhone and installing the app on iPad.
To download your In-App Purchase again, you must download it from within the installed app using the same iTunes Store account name you used for the original In-App Purchase.