They are definitely artbox? And Definitely say "8 cards per pack, look for randomly inserted cgase, costume and autographs" on the top?
First off you should buy some more and sell them to me for £50 a box.
Then of the 4 you originally have you should open at least one so you can have a base set and enjoy the fun of seeing what you find... then sell one box (to pay for the 4 you bought) then stick the 2 remining boxes somwhere and forget about them until the movie of the Goblet of Fire comes out.
Then use the money to buy a nice new house!

Roz