JackShephard is correct. No site's auction predictions ever comes close to what my league's values end up being. If its you first year, you're basically going to have to judge based off of what the first few players go for. After your first year, its best to just judge based off of what the guys went for in your league last year. If a guy gets better, add a few bucks, and vice versa.
my league uses $250 for 25 players. keeps it simple at $10 per player.
top hitters go for $35-40 and top pitchers go for around $30-35.
If you really want some custom predications, use baseballmonster.com. They'll give you values based on your league's custom scoring settings, but their values still won't be completely accurate. The market in your league will dictate the pricing.