I completely understand where your opinion is coming from, but as a big collector of Adlard WD art, I know the market fairly well.
If this is normal for prices, why did the two page splash (issue 84 pg 16 & 17) sell for over $2,500 last year? The art to issue 92's cover recently sold for $2,500.
An even greater comparison was page 16 from issue 39 (the splash where Dale is bitten for the first time). That single splash, on a 8 1/2 by 14in page sold for around $800.
I know that smaller art should be cheaper in reality, but with the WD I've noticed that because there aren't many normal 11 x 17 pages on the market, the smaller 8 1/2 by 14 in pages have been commanding similar prices. Pages from the series are minimum $100 on Mark Hays website. I don't see how a total of 4 pages, one being a splash page, would sell for this.