Wondering why the 18K Gold Apple Watch Edition smartwatch costs around $17,000, or why the base model, the Apple Watch Sport, costs $349?

You may think that the alloy that produces the Apple Watch or the fluoroelastomer wrist band for the Apple Watch Sport explains the price tag, but the gold build material is only one component of the story. To find the other, you’d have to go into something top-secret that Apple’s been working on.

This top-secret information about Apple is two years in the making, however.

News site ABC News got an opportunity to tour Apple’s top-secret fitness lab that the Cupertino, California company’s been using for the last two years. Inside the fitness, lab are Apple employees who’ve been strapping up in high-tech gear while exercising on treadmills, floor mats, and other gym equipment in order to have their workout information analyzed.

In fact, prior to the Apple Watch’s unveiling, many Apple employee has been wearing the Apple Watch (the watch covered up, according to Apple sources close to the matter) while working out on a treadmill in order to see what constitutes a calorie burned, the intensity of workouts and how they vary according to different exercises and environments, and so on.

Alongside of the fitness equipment that’s been used for walks, jogs, sit-ups and push-ups, Apple’s also created “environment rooms” whereby employees are placed in, say, a cold environment to see if a cold room can mimic colder temperatures in places around the world.

In order to create the type of environment that, say, Canada or Siberia creates, however, Apple has sent employees to exercise in those environments to get a better sense of what a workout is like for a resident in colder temperatures than say, the southern United States where Florida users, for example, are often surrounded by warmer temperatures. Calories burned and the intensity of workouts are not uniform around the world. Apple seems to be interested in tailoring workouts to personal (body type, weight, etc.) and geographic circumstances, among others.

Over the last two years, the company says that it’s conducted 10,000 workout sessions and analyzed over 18,000 pieces of data from its employees. When the Apple Watch debuts on April 24th, you can be sure that Apple’s newest and most personal device has been designed with you in mind.

The Apple Watch will arrive on the market in a little over a month and comes in three versions: the Apple Watch Sport, the Apple Watch, and the Apple Watch Edition. The Apple Watch Sport costs $349 and comes with a band that’s supposedly sweat-resistant.

Must Read: How the Apple Watch was born: Inside Apple’s Secret Lab

The Apple Watch, the middle version, starts at around $500 and comes with nicer wrist band materials (such as stainless steel, among others). The Apple Watch Edition has a starting price of $10,000-$17,000 and features an 18K gold build quality with the nicest wristbands available. Apple Watch bands range from the small price of $50 additional and go up to an additional $449.

Apple says that you can expect to pair your Apple Watch with your iPhone, but rumors persist that the Apple Watch will come Wi-Fi-enabled.