I looked on that site. They have 202 used Metris vans nationwide. About 60 have between 30K and 40K miles. I started checking and the first 10 I checked had been rental or commercial vehicles, so I just quit and I assume that most of the rest were the same.
Yep... rental returns. They bail on them about when the warranty is up. Also some may be lease turn-ins. A lot of fleets turn over their stuff after around 2 years or so. Wouldn't be alarmed; just a normal turn over cycle and not indicative of any deficiency in the vehicle.