Be patient child.  There could be many reasons your parents don't want you to buy the game, even with your own money.

It's only 45 days until Christmas, if your parents let you buy everything you want...what will they buy you.  From what you've said so far, your parents are not saying you can't have the game, just not right now.

Maybe they would prefer you save your money instead of spending it on items that you will grow bored of quickly.  Didn't you mention that you recently got a new game? 

You are just going to have to do what I tell my own children...practice your patience.