So I bought him one. Perhaps I am setting a dangerous precedent of indulgence at the grocery store, but let me tell you, never have I spent a more-appreciated four dollars. That cheap, shiny, "Hope You're Feeling Better" balloon has provided hours of entertainment.
He punches it; tackles it; races across the room dragging it by the string; accidentally pinches his finger in the clip on the end (whoops--but he only did that once and apparently learned his lesson); throws it; pushes it under the coffee table and then kicks it out with his feet; tries to feed it to his rocking horse; and generally plays with it with no activity needed on my part. I just sit there and watch him go crazy.
And that, my friends, is worth WAY more than four bucks.