Wow, I'm glad you got it sorted. That's ridiculous for an engine parts supplier to package up and ship an obviously bent dipstick. Weird, really. There must be some sort of story behind that one.
99/100 it'll be down to shaving a bit off the postage costs as EuropatcSpecial has found. Over here our postal service has some strange pricing ideas, the price you pay doesn't always go on the weight of the package also the size can trigger the next level of postage. Crazy though it sounds, you can end up paying more to send one Christmas/Birthday/Greetings card than another if one is fractionally larger and moves into the next envelope range, even if it weighs less. It won't cost any more to deliver but it'll cost you more to send it.
As for the bent dipstick, I would probably have straightened it out but made a resolution not to trust that particular dealer again. I don't like being spun a tale either and assuming that was one of the £30 items I've seen on sale, I'd also expect it to arrive ready to fit.