A young couple grocery shopping . Have you ever noticed that the prices of the things you buy online seem to change for no rhyme or reason? I was recently shopping for my daughter's first birthday, and I had my eye on the Rolls-Royce of kids' wagons — this thing is nicer than some of the cars I drove in college. But I wanted to do some research first. So I put the wagon in the online shopping cart while I read some expert and customer reviews.