Why does fundraising only ever load the last short code when it jumps to Paypal?

I have four pricing tiers, and four separate "donate" buttons but for some reason it doesn't matter which one I click (100, 250,500, or 1000,) it only loads the last one which is $1000. What am I doing wrong?!?

http://hiltondesign.net/ima/fundraising-drive/

hoping this message finds you well,

Ian