I think these specific arts, being basic lands, and the first of his being available in many many years, and the considerable quality of them, means they will realize MUCH higher prices than almost all of his other pieces. As an example, there is a reverse auction on the same page for "Rite of Passage" that is down to $825. This work is very representative of a Walker piece and much more in line with the valuation on his art in general. He has done the second most art for MtG, and closing in on #1 all time, and none of it is digital. There is a LOT of it out there. Subject matter/card quality will be the deciding factor in the valuation most of the time. I've seen a nice (IMO) piece not sell at $500 recently, and other than the basics, nothing over $2K.
FYI, I am not saying any this because I was "Street Savy" from you, but my honest opinion.