In the less expensive cars heated seats are typically only seen in the diesels. I think that this is because the people who buy the diesels often spend lots of hours on the road, like sales people as an example.

In the "Spensive" cars (Isn't that what the S stands for?) such accessories should be somewhat common.

Even if it is rare, it doesn't add any value to the car except for making it more comfortable to drive. I was one of those sales guys that ordered a new diesel MB with heated and orthopedic seats. It was money well spent. I used the heat sometimes in the middle of the summer. To stay behind the wheel for long periods, turning on the heat can be just the change you need to do away with fatigue. This is not to mention the obvious advantage on a cold morning.

Have a great day,