Hi,
For VPRS condition type based on the pricing procedure requirement type "4" assigned to the condition type. It will fetch the value from material master i.e ( Standard price or moving average price as per the setting. )
it may change at Invoice if you price type redetermine the price at billing and at that time the price at material master is change.
So check the copy control in VTFL with delivery to Billing type at item category level for price type.
Hope it will help you to understand.
Regards
Pitabash