BOSTON (AP) _ U.S. auction houses sold more than $1.5 billion worth of art last year and chalked up their best-selling season ever thanks to a broader, more educated audience, art dealers said.

Two Pablo Picasso paintings sold for more than $40 million each to become the third- and fourth-most expensive paintings ever, but the not-so-wealthy art lover also contributed to the record sales by buying works that cost thousands rather than than millions.

When the final bang of the gavel sounded on U.S. art auction sales for the season, the total came to $1.53 billion, nearly double last year's total, Leonard's Annual Price Index of Art Auctions reported this week.

The total number of art lots sold was 33,000 in 1989, down by more than 5,000 from the previous year. Experts said both the limited art supply and increased consumer interest stoked the season's record-breaking sales.

''When my grandfather ran the business, his clientele was the very top 5 percent of the upper class,'' said Abbot William Vose, president of Vose Gallery, which opened in Providence, R.I., in 1841 and relocated to Boston 40 years later.

''The clientele is very broad-based now, with even the lower middle-class buying art,'' he said. ''Art education in even grade schools, up through high schools, has played a good part in focusing attention on American art and other arts, and has made a difference in attendance at museums and art shows.''

Sotheby's Holdings Inc. in New York last year sold the third-and fourth-top moneymakers ever with ''Yo Picasso,'' a self-portrait of the artist that earned $47.85 million, and his ''Au Lapin Agile,'' which went for $40.7 million, said Robin Riley-Ahrens, the house's spokesman.

Picasso's ''Pierrette's Wedding'' went for $48.9 million in November to earn the title of the second-most expensive painting ever, but it was sold at the Drouot-Montaigne auction house in Paris and thus not included in the U.S. figures.

The world's most expensive painting, Vincent van Gogh's ''Irises,'' was sold by Sotheby's in 1987 for $53.9 million. The auction house disclosed Thursday, however, that it lent Australian tycoon Alan Bond $27 million to buy the 1889 painting; that as collateral Bond posted the picture he was going to buy, and that Bond has not paid off the loan. Sotheby's said it was abandoning the loan policy, which many critics say artificially inflates artwork prices.

''About 20 percent of the art sold at auction went for below $1,000,'' said Susan Theran, publisher of Leonard's Annual Price Index, an industry database that provides information annually on art auction prices.

''Art is affordable, and people are finding that out,'' she said. ''People are developing their tastes and buying books on how to purchase art.''

However, sales were still chiefly pushed to their record heights by purchases in the $1 million-plus market, Theran said.

Final tally for the 1989 selling season showed 240 lots of artworks worth more than $1 million were sold, compared with 84 similarly priced lots in the previous year, Theran said. Sales for the 240 lots was $779 million, more than triple the 1988 figure of $213.5 million for the 84 lots.