Hi @aboodhamwi ,
Could you please share a bit more about the 'Price List' column in your 'Price List Items' Entity? Is it the LookUp type column (generated by Many-to-One relationship)?
Based on the issue that you mentioned, I have made a test on my side, and don't have the issue that you mentioned. The screenshot as below:

The 'Normal Contact' column is a LookUp field in my TaskLists Entity, which references records from Contacts Entity. Add a Gallery within my app, set the Items property to following:
Filter(TaskLists, 'Normal Contact'.Contact = ComboBox1.Selected.Contact)
the records displayed well in my Gallery as above.
Please check if the result the PriceListId variable returns is the 'Unique Identifier' column value in your 'Price List' Entity. On your side, you could consider add a ComboBox in your app, set the Items property to following:
'Price List' /* <-- Type your 'Price List' Entity data source here */
set the SelectMultiple property of the ComboBox to false.
then add a Button in your app, set the OnSelect property to following formula:
ClearCollect(
SelectedPriceListItems,
Filter(
[@'Price List Items'],
'Price List'.'Price List' = ComboBox1.Selected.'Price List'
)
)
Note: I assume that the 'Price List' is the 'Unique Identifier' column in your 'Price List' Entity.
Please press above button, then check if the SelectedPriceListItems collection is populated with proper records.
If the issue still exists, please consider re-generate an app based on your 'Price List Items' Entity, then try above solution again, check if the issue is fixed.
Best regards,