Does "这很大钱! 再见大学钱...." make sense? Or have I written it wrong?
That does not really make sense. "A lot of" here means a great amount, while 大 means big as in size. Also 大学钱 does not make sense either. Instead you would say "大学学费" (college tuition)

So a better translation would be “这好贵啊！再见我的大学学费” (this is so expensive! goodbye my tuition)