[thecatspajamas]

To add a few more factors to Mark's list that may account for some of the price spikes you have noticed:

Family members of players will often pay a premium for photos of their granddad/cousin/father/step-uncle/etc, regardless of whether he was popular or had a long career. I have a "watch list" of at least 100 names that I try to notify interested family members if/when I happen to have a photo of their family member, and I suspect have sold a great deal more photos to family members who didn't bother to identify themselves as such (for instance, who had the same last name).

Ethnicity or nationality of players can be a factor, particularly for those who are among the first few of that group to play in the majors.

The photographer, if known, can add a level of desirability, though it is often difficult to discern how much of the value is based on the pedigree vs. the quality of image for which the photographer is known for (in other words, is a Burke photo of a player worth more because it has Burke's name stamped on the back, or because the image that Burke typically produced, even of no-name players, is of a higher quality than most of his contemporaries?)

The team that the player is associated with - just about every team has die-hard collectors who will pay more for anyone in the uniform of their chosen team, and some teams simply have more fans than others. When you're selling, you just have to hope that at least 2 die-hard fans are duking it out for your photos.

Obscurity - goes along with the one above - if someone is looking to put together a collection of every player to play for a particular team, the guys who were only in that uniform for a short time can command a higher price than their stats might lead you to expect simply because there are not many images of them in that uniform


Bottom line is, it all comes back around to what Mark and others have said in that you should collect what you like first and foremost. You could go crazy trying to figure out why one particular photo went so high, and even if you do decipher who is bidding on it and why, there is no guarantee that the next time a similar photo comes up one of the main competitors won't be away on vacation or something, resulting in drastically different results. Looking at only high-quality images of HOFers by famous photographers can give more predictable results, because there are always many eyes on those types of photos which takes out some of the variability, but even in the deep end of the pool there are still spikes and dips in prices.