In reply to:
That's true, though I agree with Jewels in that it's a little unclear to me whether you'd use an affiliate linking image with a promo code because the affiliate link image wouldn't say anything about the promo code itself. Or do you think it would make sense to use the image for a link that encoded a promo code?
After having a think about what I posted, I have to agree with both you and Jewels, the banners would be confusing to someone who is not in the know about Dreamhost's promo codes, and also using an encoded promo url on the banner is not really ideal either since the image quotes the price which would be different from the banner when using a promo code. I guess Dreamhost should now pick some quotas, and change the banners to match to remove the confusion.