I don't know how much it cost but I don't remember having an elaborate graduation party. The kids who had them were kind of the weird spoiled kids who were rude or full of themselves and had something to prove? 
We have an in-ground pool and I had friends over, we swam and hung out and my dad grilled a bunch of hot dogs and we had toppings out, some chili, cheese, relish, mustard/ketchup...I think that was about it. And my mom made a big thing of pasta salad, I think we got some chips and soda and she made a cake.
Decorations I'm not sure we did any, maybe a banner from Wal-mart? And then we bought a bit lot of rubber ducks in mortar boards from Oriental Trading and tossed them in the pool for the day and everyone took a few home as favors.
Oh I also had a white stuffed dog with a mortar board and a bunch of sharpies so my friends could sign it. I'd be surprised if we spent much more than $100. Knowing my mom she probably grabbed everything at BJs for pretty cheap.

We have an in-ground pool and I had friends over, we swam and hung out and my dad grilled a bunch of hot dogs and we had toppings out, some chili, cheese, relish, mustard/ketchup...I think that was about it. And my mom made a big thing of pasta salad, I think we got some chips and soda and she made a cake.
Decorations I'm not sure we did any, maybe a banner from Wal-mart? And then we bought a bit lot of rubber ducks in mortar boards from Oriental Trading and tossed them in the pool for the day and everyone took a few home as favors.
Oh I also had a white stuffed dog with a mortar board and a bunch of sharpies so my friends could sign it. I'd be surprised if we spent much more than $100. Knowing my mom she probably grabbed everything at BJs for pretty cheap.