The era when a four-bedroom house could be built for $1,500 is long gone, but it isn't being forgotten. Yes, $1,500 is correct.

Antiquity Reprints, a publisher in Rockville Centre, N.Y., is keeping that era alive in a thin, softcover book called "Shoppell's Modern Houses" a collection of house plans and drawings originally published in 1887.

The most practical lesson to be drawn from this book is that the cost of houses now is approximately 50 times what it was 92 years ago. A house equivalent to the $1,500 residence built in 1887 would probably cost $75,000 today.

But "Shoppell's Modern Houses" should be read for practical lessons. It should be read for its priceless insights into another age, when large houses cost $3,000 to build. And there were no gasoline shortages, nuclear weapons or DC-10 crashes.

Along with drawings and floor plans of 18 late-Victorian houses with construction prices of $1,200 to $12,000 there are articles on such fascinating subjects as "Sideboards and Dressers" and "An Ice House and Cold Room."

The $12,000 house, incidentally, is a three-story mansion complete with balconies, library and sitting room, a 10-foot-wide hall, verandas in front and back, bay windows, pantry and woodshed. "The ceilings of the hall and dining room show the timbers," says a description accompanying the drawing, "and are paneled with red baywood, or what is commonly known as and passes for mahogany. The wainscoting and trim throughout the first story are of the same wood. In the attic, besides the large hallway, there is a billiard room 14 feet by 22 feet and two large bedrooms."

Even in 1887, however, some things cost extra. If a full basement with stone or brick walls was wanted for the $12,000 mansion, the buyer had to come up with an additional $450.

The article on plumbing estimates the cost of fitting out a new house with a water closet (toilet), bathtub and basin at about $375.

The material in the 32-page, large-format book was taken from a 19th-century magazine of the same title published by a group of architects headed by R. W. Shoppell.

"Shoppell's Modern Houses" cost $5 and can be ordered from Antiquity Reprints, Box 370WS, Rockville Centre, N.Y. 11571. An 8-by-10-inch sepia engraving of a Victorian house is included with each book, and there is a money-back guarantee.