How much does it cost for a return flight from Weifang to Beijing and is it practical for like a weekend trip?

As I know, the air tickets' price varies from time to time. Also the flight between does not fly every day. So it is hard to tell you the exact cost. When will you travel for this journey anyway? You can search the flight schedule and price at the website according to your requirements:
https://www.travelchinaguide.com/china-flights/