[Lordstan]

There are no specialized ball sellers per se. Most autograph dealers sell a wide variety of items that are signed.

As far as a price. I think $300-500 is probably a reasonable range to expect for a decent signed Mantle baseball. It certainly could be much higher. If the ball was a ball in perfect condition, has a special inscription, or comes from UDA, as DRC mentioned, it can draw a premium price. I wouldn't expect to pay that for a smudged one.

I think my advice for you is probably similar to if a non card collector came to you for advice about buying a certain type of card. I think most would probably say to do some research on what they want, what the prices are, and then find a reputable dealer to deal with.

My recommendation on those two dealers stands. Both are fair and honest. If they don't have want you want, I know they point you in the right direction.

Good Luck,
Mark