Every business eventually has to reckon with the tool that makes its own work cheaper to do.
For Wall Street, that tool was the spreadsheet. For Madison Avenue, it was the internet. For the world’s most expensive consulting firms, the tool is artificial intelligence, and the reckoning is already underway.
For three decades, the business model at McKinsey & Company, Boston Consulting Group, and Bain & Company has rested on a deceptively simple premise.
Clients pay top-tier consultants by the hour or by a fixed project fee that maps to a team’s expected time on the case. Junior consultants do the research, build the slides, and crunch the data.
Partners sell the story. Bills run into the millions, often without an explicit promise that the strategy will actually work.
That model is now bending under the same technology these firms have been hired to roll out for everyone else. AI tools are compressing the hours it takes to do the underlying analytical work, and the Big Three are quietly rewriting how they charge for it.
How AI is rewriting the McKinsey fee model
Speaking to reporters at a London media event in November 2025, McKinsey’s UK managing partner Michael Birshan said, “We’re doing more performance-based arrangements with our clients,” according to Business Insider.
About one quarter of McKinsey’s global fees now come from this kind of outcome-based pricing, the consultancy disclosed at the same briefing.
The shift is not subtle. Rather than asking what a defined scope will cost, clients now arrive with the outcome they want and ask McKinsey to price its work against actually delivering it.
More AI:
- Micron sits at the center of a red-hot chip rally
- IBM CEO sends blunt message on AI and quantum computing
- Anthropic CEO makes shocking admission about AI
“This is a moment where many of the fundamentals of the professional services model are coming under challenge,” McKinsey’s global leader of technology and AI Kate Smaje said in the same briefing, per Business Insider.
What struck me when I looked at McKinsey’s own framing is how much of the pivot is being driven internally, not by client pushback.
The firm’s enterprise AI assistant Lilli now runs more than 500,000 prompts a month inside McKinsey itself, with consultants reporting up to 30% time savings on knowledge work, according to Hunt Scanlon Media.
When your AI is doing nearly a third of the thinking, the billable hour starts to look less like a measure of value and more like a tax on inefficiency.
Related: Big Four firm cuts 100s of jobs as consulting demand slows
Why the billable hour quietly broke at Bain and BCG
Bain and BCG are walking the same road, just from different angles.
Bain & Company has been the most direct about its AI exposure. In a May 2026 announcement, the firm said its OpenAI partnership has now stretched to more than three years of joint client work, capped by an investment in OpenAI’s new Deployment Company alongside private-equity backers TPG, Advent, Bain Capital and Brookfield, according to Bain.
The same firm has previously said that AI- and tech-enabled revenue accounts for roughly 30% of its consulting business, with leadership projecting that share to climb to 50% in the coming years, per Bain.
BCG, for its part, has told investors it expects AI work to provide roughly 20% of 2024 revenue and roughly 40% by 2026, CEO Christoph Schweizer said at the firm’s investor briefing, as reported by industry newsletter The 80/20. For a roughly $12 billion firm, the math implies AI-tied work running into the billions per year, with the curve steepening every quarter.
Meanwhile, around 150 former consultants from McKinsey, Bain and BCG have already been contracted to train AI models to perform entry-level consulting tasks, Bloomberg reported. The people who used to bill those hours are now being paid to teach a machine how to replace them.
What outcome-based pricing actually means for clients
Outcome-based pricing is what it sounds like.
The client and the firm agree on a measurable goal, such as revenue growth, cost reduction, or a specific operational metric, and the fee is tied to whether that goal is hit. A floor of fixed costs usually remains, but the upside and the downside now sit on the consultant’s side of the ledger.
It is a model the consulting industry has flirted with for years. AI has finally given it a reason to scale.
The numbers behind the shift do most of the talking:
- About one in four of McKinsey’s global fees are now tied to outcomes rather than hours, McKinsey UK managing partner Michael Birshan told reporters in November, per Business Insider.
- Bain’s tech- and AI-enabled revenue has reached roughly 30% of the firm’s business, with leadership projecting that share to climb to 50% in the coming years, according to Bain’s announcement of its partnership with AI researcher Andrew Ng.
- Around 150 former consultants from McKinsey, Bain and BCG have been contracted to train AI models to perform entry-level consulting tasks, Bloomberg reported.
I ran the rough math on what that means in dollar terms. If a typical MBB engagement once cost a client $300 to $500 per consultant-hour at a blended rate, per industry pricing data from DCF Research, even a 25% AI-driven speed-up effectively claws back a portion of that fee for the client, but only if the consulting firm gives it up.
Outcome-based pricing is the polite way of saying the firm now has to actually share the productivity dividend.
What the AI consulting shift means for your portfolio
The change matters far beyond Park Avenue.
If McKinsey, BCG and Bain cannot defend the billable hour, neither can most of the white-collar industry that mirrors them. Law firms, advertising agencies, accounting practices and even some enterprise software vendors are watching the same pricing logic come for them.
The “service-as-a-software” model that EY’s Tushar Sharma described to Business Insider, in which clients pay for results rather than hours, is the direction every margin-rich knowledge business is moving.
For investors, the read-through comes in two parts.
The publicly traded consulting and IT-services proxies, including Accenture (ACN) and IBM (IBM), face a margin question that will not go away. Their pyramid models depend on the very leverage AI is now flattening.
At the same time, the corporate clients of these firms, effectively most of the S&P 500, are about to get more measurable value per consulting dollar, which should show up in their own operating margins long before it shows up in any consulting firm’s press release.
The irony is hard to miss. The Big Three made their fortunes telling Fortune 500 boards to “transform” themselves around technology. Now they are being forced to do the same thing first, and in public.
For anyone watching consulting fees show up on a quarterly earnings call, the question is no longer whether the model will change. It is who pays for the change first.
Related: McKinsey says AI could reshape how you buy insurance
