Amazon Prime Account - Is It Worth It?

As I continue to review my money situation, I am trying to make sure that all of the programs I am a part of are really worth it.

Today, I'm looking at my Amazon Prime account, due for renewal in November.  The Prime account gives me free 2-day shipping on eligible orders and $3.99/item shipping on next-day orders.

Cost/year: $79
Orders placed with Amazon last year: 118
Orders that I would have had to pay at least $3.99 shipping on (2-day shipping): 60 
Items that I would have had to pay at least  shipping on (next-day shipping): 15
Total saved in shipping: $239.40 + $67.35 = $306.75

Total savings of: $306.75-$79 = $227.75