Chad,
Like all smaller sets, say 20 to 50 cards, there are always certain ones that are harder to find that add to the uncertainty of what is a "fair" price. As previous posts have stated, the specific player, colored background, and condition might add to the high or low price of a particular card.
30s and 40s are pretty high grades for E98s and do command a little higher price. (For example, of the 958 E98s graded by SGC, more than half 486, are A's 10s and 20's)
Just going by SGC pop reports, each player has a pop ranging from 21 for Vaughn to 44 for Wagner with most of the players somewhere between around 30 or so each.
Then the pricing can really get crazy if you add in crazy people like Pete
and I or anyone else who is fanatic enough to go after a Master Set of them with each player with all four of the colored backgrounds. (Hey Pete, I mean that as a compliment, Hope things are well!). Some of the cards you see seem to come up for sale all of the time with a certain colored background- Green McGraws and Red Mathewsons come to mind and are easy to obtain if you can afford them. Other player/color coimbinations rarely come up for sale. Heck, there are a few combos that I have NEVER seen before, so who knows if anyone will ever master this set.
Sorry I rambled on about E98s, but I also agree with others in that $300 or maybe a little less would be a reasonable/ fair price for an Evers in 30 condition.
Best wishes on your collecting.
Tim Kindler