"Art for All: American Print Publishing Between the Wars," at the National Museum of American Art (formerly the National Collection of Fine Arts), is, in many ways, an exhibition about cash.

The most coveted of the 71 impressions here -- by such beloved masters as Grant Wood, Edward Hopper, John Sloan and John Marin -- were once amazing bargains. "Night Shadows," for example, that moody Hopper etching, is now thought a classic, and at auction might fetch $5,000. But when it was first sold by the New Republic magazine in 1924, it was almost free.

That year, to lure readers, the New Republic offered a portfolio of Six American Etchings to its new subscribers. The signed Hopper was included, so were prints by Sloan and Marin -- a group of prints now worth perhaps $9,000. Then, they cost $8 -- and for that one got not just the etchings, but a year's subscription, too.

Between 1918 and 1938, new prints sold by mail through other artists' groups were not much more expensive. Membership in the Contemporary Print Group cost only $15 in 1933. For that sum, one received half a dozen lithographs -- by such artists as Orozco, Reginald Marsh and George Grosz. lThe lithographs distributed by Associated American Artists in the 1930s were a little dearer. Thomas Hart Benton's "I Got a Girl on Sourwood Mountain" (1938), Grant Wood's "Fertility" (1939) and "Angry Skies" (1935) by Louis Lozowick cost $5 each -- though if one ordered six prints, the sixth was thrown in free.

The American Artists Group, which was organized in 1934 to popularize American art by "taking it out of the luxury class," offered pictures by Paul Cadmus, Lozowick and Rockwell Kent for $2.75 each. These prints, however, were not signed. Curator Janet A. Flint, who organized this show, writes that that omission "caused considerable unhappiness. . . . The brief but lively controversy that followed prompted Rockwell Kent to offer his signature to any purchasers of his prints for $10 -- but he counseled them not to waste their money."

Ten dollars was in those days quite a lot of cash. In 1937, plump portfolios containing 30 offset lithographs were offered to the public by The American Abstract Artists for 50 cents apiece -- or about 1 1/2 cents a picture.

Bargains of that sort were in part a reaction to the inflated print prices of the previous decade. In the 1920s, writes Flint, "collecting was too often dominated by a fondness for specious rarity and preciousness that at times bordered on the absurd. The addition of a few strokes to the plant by a popular English etcher, for instance, could produce a unique artist's proof that commanded even higher prices than his already artificially limited edition. . . . Much of this attitude ceased abruptly, however, with the onset of the Depression. For many people, original works of art now became a luxury they could no longer afford. Moreover, many collectors who had purchased artificially rare, overpromoted and overpriced etchings in the free-spending, speculative '20s, now found themselves holding financial duds. . . . Clearly, new measures were needed if the American printmakers were to survive."

One response was mass production. The artists' groups that formed in the 1930s produced large editions of 200 prints or more. Their motives were at once generous and selfish. They hoped to build a new art market that would increase their sales while making inexpensive art available to all. We are still in their debt: The seeds of the print market that blossomed in the '60s were planted in the period covered by this show.

The artists of the '30s were hungry for acceptance. The prints that they produced may seem a little timid to the modern viewer's eye. Most of them aren't daring, difficult or shocking. A few of them are funny. Peggy Bacon's "The Promenade Deck" is chock full of gags. Some of the prints are thrilling. Will the trapeze artist in "The Missed Leap" by John Steuart Curry be caught by her partner, or is she to fall? Many more are picturesque. Grant Wood's proud white barn, and the lovely wood engravings of moonlit coves and Vermont hills -- published by The Woodcut Society of Kansas City, Mo. -- would look perfectly at home on any farmer's wall.

During the Depression, many of these printmakers, particularly those of The Contemporary Print Group, were artists of the left. The lynched "Negroes" of Orozco, William Gropper's "Sweatshop," and the Thomas Hart Benton's "Mine Strike," are pictures made by men who felt it was their duty to mix politics and art.

But he who serves the masses has to pay price. Many of these prints seem a bit too preachy and peculiarly impersonal. By the time that one encounters the playful wackiness of Alexander Calder's "Score for Ballet 0-100," or the undisguised homoeroticism of Paul Cadmus' "Going South," one is strangely grateful for their self-indulgent art.

"Art for All: American Print Publishing Between the Wars" closes on May 10.