Although I don't see a way to test it, I'm guessing that the payment page itself is secure and does use SSL but the sales pages don't. Probably using stripe.com directly instead of hosting the forms locally.

Edit: Okay, I was wrong and right at the same time. The page itself is not secure just http. It does, however, have an iframe with the stripe CC stuff in it. That is served over SSL, so the data is encrypted. The user just can't easily tell.