If you want something a little cheaper:
We are the original producer of the famous Pea Sheller Jr. (Mr. Pea Sheller) and its larger electric "daddy", the Electric Pea Sheller Sr.! Shell peas FAST!
www.leemfgco.com
I have their smaller model I bought at a yard sale for $3 still in the box. It is perfect for me and I've shelled a ton of purple hulls with it over the years. You can hook a drill up to it but I just crank it by hand. I grow the vining variety that gives you peas all summer long but at a slower pace so I shell every two or three days. If you have a truck patch, you might want something bigger. I'm too busy to shell by hand.
I prefer to let my peas set a day or two before shelling but if they get too dry, shellers won't work. If you can find an old wringer for laundry, they work too. I have one displayed in my big bathroom along with my rub board collection. Daddy was always trying to get me to use it to shell peas with but it's too pretty for that. I may need it for laundry some day.