Dean,
You have a Mantle 1947-1966 Exhibits card with no pinstripes and white outlined name batting variety. I did a quick search on eBay - as you probably did - and found a wide range in prices. One of the issues with Exhibits - as in fact a number of other pre-war cards - is that a number of reprints were made, including the Mantle batting pose. Unless the cards being sold are either graded by a third party grader that is respected within the industry or seller includes back scans (see link on how to differentiate between originals & reprints) or other warranties to insure to possible sellers the card is an original, prices can vary significantly.
I have purchase several Exhibits, some of which turned out to be reprints. Reprints generally have a gray back. Following are a couple of links to some Exhibit reprint & general info articles from the archives:
http://www.net54baseball.com/showthread.php?t=117276
http://www.net54baseball.com/showthread.php?t=118564
There are also a number of good posts by Adam W, Frank W and Scott M - all of whom collect Exhibits and know a lot more about the issues than I do. Nice card, but sorry I can't help you on price. It looks like you have a high quality card with sharp corners. Maybe Adam, Frank or Scott will chime in.
Zach Wheat