The market determines what is more valuable. The market determines what is more desirable. But the market has no say on what is a first appearance. That is determined by the content. I'm not trying to knock down Hulk 181. I'm simply pointing out that the fact that 181 is not Wolverine's first appearance is going to have a negative impact on where the book would fall amongst keys in the hypothetical situation you're proposing. If a one-page (it may be one panel, but it's a full-page panel) appearance was irrelevant, then Hulk 180 would be no more valuable that the other common issues in that run of Hulk.
Based on what you're saying now about the market, it seems what you're looking for is not where a hypothetical Silver-Age Hulk 181 would rank amongst keys, but rather where it would rank in dollar value.