Not at this time (by which I don't mean that they sometimes do, but rather that they haven't yet offered special DVD prices for Steam customers).
The Telltale Store often has sales (like this one
last December) where you can get their games for cheaper, but the price would be the same for Steam and non-Steam customers.
I am a community moderator, here to assist, keep the peace, and keep these boards clean and friendly for all. I am a volunteer, and not a Telltale employee, and my opinions are my own.