Miracle Whip vs. Mayo

So Friday night, my sister was over helping me put away groceries when I realized that I had just bought a 5 lb bag of potatos and my husband had bought a 5lb bag of potatos earlier that week. What in the world were we going to do with 10 lbs of potatos!!! I called my Grandma because she is literally known for her amazing potato salad. I figured it was the only logical thing to do - make potato salad and bring it on our weekend trip to Michigan. Dennis was still out at his brother's helping him with some flooring so I called and asked him to please bring me a large can of Miracle Whip and a dozen eggs when he came home. I stressed the fact that I needed Miracle Whip for my grandma's recipe. Well at about midnight, he comes wandering in with the largest jar of mayonnaise I have ever seen and no eggs. Since we were leaving by 9am for Michigan the next morning, there wasn't really time to go back to the store and get the ingredients I needed. Needless to say, I still have 10 lbs. of potatos. My argument is that he just didn't listen to me. His argument is that miracle whip and mayo are the same! Please tell me that is the nuttiest thing you have ever heard. I for one HATE mayonnaise and LOVE miracle whip. He thinks I am crazy now. Since the "grandfather sized" mayo cost about $8.00 I have sent him to return it and get the money back. I don't think I will ever use that much mayo in my entire life. yuck!