Gladwell was arguing that it takes 10,000 hours to go from a knowing nothing to becoming a master at any craft. At 8 hours a day, every single day, is ~3.5 years.
For programmers, most of the initial chunk of that time is through hobby programming or through formal training at a college or the like. That's 3000 hours that the company didn't pay for. That's probably the experience most programmers walk in to any company as a Jr Developer, and they are paid accordingly. Nobody is being offered $150k/yr with that level of experience. Maybe $30-$40 depending on where they are working, and then are promoted and given raises above that.
When I say $75 an hour including overheads I don't mean a salary of $150,000 - I mean a salary of $60,000 plus tax plus health insurance plus pension contribution plus office space plus a desk plus a computer plus the calls to IT Helpdesk plus the line manager's time plus any commercial software plus other developers' time coaching plus the 20% cut paid to the recruiter plus the HR and payroll people's time plus networking and internet connection plus the backed up storage space on file and mail servers plus the car parking space plus a phone line plus cleaning plus the break room food and coffee.
Of course these things are company-dependent, but I'm a comparatively junior developer and for purposes of internal costing my employer costs my time at $75 an hour.
When your developers cost $75 an hour including overheads, paying people for those 10,000 hours is an extremely costly proposition.