Most people are motivated by more than money. Working in product development at a place like Apple, or Google, or Amazon, etc, gives you a chance to work with very smart, accomplished people. It gives you license to do great work and maybe push some envelopes with what is possible in your field. It gives you a platform to have a major impact on society. It makes other people say "wow" when they hear where you work, or what product you helped create.

For some people that is a form of motivation, and even a form of compensation. Doing graphic design at a PR agency for a cereal campaign, even if it pays more money and gives more vacation time, might be less attractive to people than a harder, more demanding job that confers the above benefits.

It's also important to look at the entire career. Busting her ass at Apple for 6 years might set up a young designer to get taken very seriously if she decides to move to another company, or start her own. That would be less true if she was a junior designer working hourly for Brauny paper towel company (or whatever).