Every engagement carries two kinds of cost. The first is obvious: the time you spend actually doing the work. The second is everything around the work - finding the client, scoping the job, sending the proposal, chasing a reply, opening the file, following up on the invoice, sorting out a misunderstanding. Economists call these transaction costs: the cost of doing the deal, separate from the cost of doing the work.
They rarely appear on an invoice. They never appear on a timesheet. And that's exactly why they're dangerous - they sit outside your cost structure as you normally think about it, so you can't manage what you can't see.
A factory spreads its transaction costs across thousands of identical units. The professional services business model doesn't work that way:
Every engagement is a fresh negotiation — a new scope, a new client, a new set of expectations to align.
The person who does the work usually sells it, sets it up and chases payment too — so transaction costs come straight out of your billable capacity.
The costs are front-loaded and back-loaded — heavy at the start (winning and onboarding) and at the end (billing and collecting), while the value only lands in the middle.
That shape means a small, low-value job can carry almost the same transaction cost as a large one - but earns a fraction of the fee to absorb it. Understanding this is the foundation of a profitable professional services business model.
A quick tour of a typical engagement, split the way your cost structure actually behaves:
Before the work: prospecting, calls, scoping, proposals, negotiation - and the deals that don't close (their cost is real too).
Setting up: onboarding, conflict checks, engagement letters, collecting information, systems and access.
During: coordination, status updates, re-scoping when things shift.
After: billing, follow-ups, collections, and the occasional dispute.
None of it is the work your client is paying for. All of it is an indirect cost that eats your professional services profit.
Transaction costs aren't a sign you're doing something wrong - they're the natural friction of being in business. But left unexamined, they set an invisible ceiling on your margin. The Professionals who thrive aren't necessarily the ones charging the most; often they're the ones who've quietly stripped the friction out of every engagement.
Over the next four posts we'll put a number on that friction, show how small reductions compound into serious margin, look at who's already forcing you to carry their costs - and how you can turn the tables.
Check out our guide to Profitability in Professional Services here.