If it wasn't converting, Clickbank would have shut down a long time ago.
And not to mention the many vendors and affiliates banking well.
I'm doing relatively well with Clickbank offers too. It still converts. Also, most vendors are now doing video sales letter (VSL) than the old written sales letter (WSL). And if you ever notice, all the top offers' VSL are very well made.
Without a doubt, to a marketer or someone who knows about marketing hype and all, it wouldn't convince them at all and these VSL/WSL would just look scammy. But put yourself in the shoes of a non-experienced marketer, they would be intrigued and would continue to watch throughout or read the newsletter, especially if they are seeking for answers to their problems - whether is it weight loss, relationship guides, survival, yoga, and so on. At the end of the day, it is how you market your products or promote them.
And that is also why most vendors are offering physical copies along with digital copies. If it is just digital copies, they would set it at a more realistic price (say, $19 rather than $39 or $47 like in the past. If not, they slap that exit-page discount.).