When John Snyder paid $600 for a Donald Duck comic book four years ago, his wife thought he was crazy. A year later, after he sold the rare 1940 issue for $1,000, his wife told him to buy more.

This week the 36-year-old government relations specialist from Alexandria made a record deal for what several experts say is the most valuable comic book in the world. After five hours of negotiation, Snyder paid $13,000 (or $8,600 an ounce) for a 1939 near-perfect copy of Marvel Comics No. 1 that he will never read.

"The dealer wanted $15,000, so I was lucky to get it," he said. "I know people think that's crazy. When a noncollector hears that kind of price he just can't comprehend it.

"But as a collector it's extremely important, and as an investor you want to put your money into something that will be worth more later. The way the stock market is going, you've got to get whatever you can."

Snyder has cleared $17,000 profit since he started buying and selling comics in 1975. He is convinced he could sell "the book" for $19,000 next year, if he decides to part with it.

"If I put that same $13,000 in certificates," he noted, "the best i could hope for would be $14,000 in a year. You tell me who's crazy."

An estimated 100,000 to 200,000 people -- from grandmothers to young kids -- collect comic books, according to Robert Overstreet, who publishes the Comic Book Price Guide. A comic collector's bible that sold out its press run of 50,00 copies earlier this year, Overstreet's guide lists the value and content of every American comic book published since 1903.

"Comic books have always been an excellent investment," said Overstreet, who claims that the number of collectors has skyrocketed from 2,000 in 1970. "In recent years they've been averaging more than a 25 percent increase in price per year. Some people have put themselves through college selling comics) $."

Several factors contribute to a comic's worth.

"First appearances of characters that have become popular and have lived on, like Superman and Batman, or first appearance of major villians are valuable," Overstreet said. "Rarity can play an important role if the comic has something else going for it, too. If there was a low distribution, a good book can be worth more."

The work of certain comic artists also affects the price. For example, Carl Barks, who wrote and drew Donald Duck, has literally millions of fans throughout the world. According to Overstreet, a $100 investment a Donald Duck in 1971 is now worth about $2,700.

"Condition is extremely important," he added. "The very valuable books have to be in perfect condition -- no creases, completely white pages and not the slightest cover flake. Most of these were unread and put in a file when brand new."

Snyder's prized comic contains the debut of superheroes Sub-Mariner and the Human Torch. It is one of an estimated 25 copies known in existance, only three of which are in almost as good condition, Snyder said. His issue stored with a chemically treated board in a plastic sleeve, has probably never been read.

"If you read it, you're likely to bend or crease the cover, which hurts the value," said Snyder, who purchases cheap reprints so he can read the stories. He has never read most of the estimated 175 comics in his collection.

Next to his "marvelous Marvel, "SnyderS favorites are his Batman No. 1 and Captain America No. 1, each of which is worth about $3,000. To protect the collection from theft and from the destructively curious fingers of his 3-year-old daughter, he keeps it in a bank safe deposit box.

"Part of the attraction for me is the nostalgia," said Snyder. As a child, he collected comics, which he sold for a nickel each after he discovered girls -- "the dumbest move I ever made.

"Comics bring back that sense of wonder I had as a child. This hobby is pure fantasy. Even in a recession comic values won't go down because people need that escape.

"I never dreamed I'd start collecting comics again," he said, "But when I went to a comic convention with my son, who is an artist, and saw two elderly people haggling over trading Mickey Mouse for Donald Duck I began to discover how many people are involved and how profitable it can be.

"Plus comics have artistic value -- they are one of the few art forms that originated in this country. And you can pick up a lot of history reading them."

For Snyder, the toughest part of collecting is selling. "But when you're investing and have responsibilities, you can't keep them all or go wild and buy everything," he sighed. "You've got to be professional about it, study the market and talk to dealers.

"But it does bring out the kid in me," he said, grinning. "Everybody in their life would like to own something that is number one in the world. And I did it."

Comics dealer Stephen Geppi is still a bit stunned from the deal.

"I've seen 'em all, and that book's the best," said Greppi, owner of three Geppi's Comic World stores in the Washington-Baltimore area.

"You make the biggest sale ever, and everyone thinks that's so great, but in a way it's a heartbreak. I had it for about two years, and unless you're a collector you don't realize what it's like to own the best.

"We were up until 1:30 in the morning the night he bought it. But it's my business and unfortunately you can't keep'em all." CAPTION: Picture, John Snyder and $30,000 worth of comics, by Lucian Perkins -- The Washington Post