Not sure how I missed this thread . . .
I agree with Jay and others. Very few collectors focus on error cards, the buyers are typically advanced set or team collectors who have expanded scope to include some of the correct and errant variations. The more significant mis-spellings garner a bit more interest, particularly those that rarely show up. Sometimes the mis-spelling is co-incident with a tough pose or team change variation and the card then certainly commands a healthy premium but its the rare pose or team change driving the value more so than the misspelling.
With McGreachery, its my belief that much of the value isn't so much due to the name on the card, but instead the subject matter (Deacon White) and the pose rarity. Deacon White's portrait is among the toughest poses in the OJ set and would command a significant premium regardless of whether the card named him as McGreachery or White.
I think the card's value would edge out Wright's rare portrait since Deacon has but one portrait pose, Wright has three different portraits, one being nearly identical to his rarest pose. Generally speaking, White is also more difficult subject matter than Wright (tougher to find one of Deacon's 9 poses than one of Wrights 3). Add on any potential bonus for the McGreachery mystery and I think it rises to the second most valuable card in the set (behind Anson in Uniform).
But your run-of-the-mill mis-spellings such as Shindle/Shindel, Weidner/Eidner, Swartwood/Schwartwood, etc. etc. command little if any premium. Even the comedic examples such as Genins/Genius command little premium because it is so common (supply and demand). That stated, I'm willing to pay a premium for any Detroit errors
