Having followed the steps in the Uninstallation Guide, if you are unable to uninstall Flexpricer due to the error “This installed component is referenced by a locally created component.” then you likely have records in your Salesforce organisation that are assigned a record type included in Flexpricer.
Salesforce prevents an app from being uninstalled if a Record Type provided in the app is assigned to existing records. This is outlined in their support article here: https://help.salesforce.com/articleView?id=000351179&language=en_US&mode=1&type=1
If the records displayed in the error are already deleted, you should empty your Recycle Bin, or wait 15 days for the records to be permanently deleted.
If the records displayed are not deleted, then follow the steps in Salesforce’s support article above to change the record type on existing Contract records from ‘Subscription’ (the record type provided by Flexpricer) to a locally created record type (e.g. you could create a record type that’s specific to your Salesforce Org called ‘Standard’).