How much should we pay to play in the great outdoors? More than we do now, say government auditors. A report by the federal General Accounting Office finds that the Forest Service loses millions of dollars each year by not charging enough to private and commercial recreationists. Investigators say the outdated permit fees charged to ski areas, commercial hunting guides and rafting companies don't even cover the cost of processing. Church and other groups are also undercharged, they found, and if the Forest Service figured current land values into its 30-year-old pricing system, the fee to use a recreational lot in a national forest could triple. For a free copy of Fees for Recreation Special-Use Permits Do Not Reflect Fair Market Value call 202/512-6000 or write U.S. General Accounting Office, P.O. Box 6015, Gaithersburg, MD 20884-6015.