Ikea found ways to produce its iconic Billy bookcase more cheaply over the years. (Ikea)

The ubiquitous Ikea Billy bookcase, which has graced the walls of millions of first-time homeowners and apartment dwellers, turns 30 this week.

The much copied, bought, sold and traded bookcase was born on the back of a napkin in 1979 after an Ikea advertising manager named Billy Liljedahl complained to a designer that he simply wanted "a proper bookcase just for books."

Forty-one million bookcases later, the Billy has become a household name. And it's likely one of the few furniture designs that has actually gotten cheaper over time, dollar for dollar.

Swedish-born designer Gillis Lundgren, who also founded the Ikea flat-pack concept, dashed the first sketch of the Billy on a napkin, noting at the time: "Ideas are perishable and you have to capture the moment as soon as it arrives," according to a news release.

Lundgren named it after Liljedahl, and today 3.1 million of the bookshelves are produced in Sweden each year, and it seems there's no sign of sales slowing. In Canada, about 250,000 are sold every year.

When the Billy bookcase was introduced to the Canadian market in 1979, an 80-centimetre white Billy cost $98. Today, it goes for just under $70, and even cheaper than that if you visit online classifieds like Craigslist or Kijiji, where used Billys can be had for $15 and less.

Ikea credits the price drop to design revamps and the use of cheaper materials. The original Billys were made of oak and pine. Today, they're constructed of pressed-wood and laminates.

The first Billys were also 10 centimetres wider. Reducing the width made it lighter and lowered costs for raw materials and transportation. The concept of flat-packing further reduced costs.

"Flat-packing, continuous product development, more efficient production methods as well as increasing volumes, has allowed Ikea to make Billy even more affordable today than 30 years ago," Kerri Molinaro, president of Ikea Canada, said in a news release.