it's hypothesized that part of the reason that tulip prices rose as quickly as they did was that it took 7-12 years to grow new tulip bulbs

Also, one of the curious aspects of the tulip-breaking virus is that the patterns only temporarily breed true; so the supply of particular tulips is inherently limited both by how long it takes to grow them and by how many generations you'll get before the coloring disappears from offspring. (This is why when you read about Tulipomania, you'll usually see old illustrations of specific tulip varieties and not photos of modern plants - because they're all gone, they no longer exist.)