We've done margin. We've done pricing. Which means we've arrived at the part everyone saves for last, costs. Not because it's the least important. Quite the opposite. It's because looking at your costs properly means confronting some things most business owners would rather not see.

So let's see them.

The problem with costs is that they're quiet.

Pricing is uncomfortable. You feel it when you quote someone. You feel it when a client pushes back. There's friction, and friction gets your attention.

Costs don't work that way. They just sit there, accumulating, doing their thing. A subscription renews. A supplier puts their rates up. You take on someone to help and absorb the cost without adjusting what you charge. Each thing, individually, feels manageable. Together, they quietly eat your margin alive.

This is what I call cost creep. And almost every business I look at has it, to some degree.

There are two types of costs. Most people only think about one.

• Fixed costs are what you pay regardless. Rent, salaries, software, insurance. The bills that land, whether you've had a good month or a terrible one.
• Variable costs move with your output. Materials, subcontractors, delivery, commission. The more you sell, the more they cost.

Software deserves a special mention here. We're all drowning in subscriptions, tools that seemed essential when you signed up, auto-renewed quietly ever since, and are now just a line on a bank statement nobody looks at. I'm as guilty of this as anyone. It adds up faster than you think, and it's almost always the first place I find waste when I sit down with a business's numbers.

Knowing the difference matters because it changes how you think about decisions. Taking on a new client when you're at capacity might mean variable costs that eat most of the margin. Dropping a client when your fixed costs are covered might cost you less than you think.

Most people know their fixed costs reasonably well. It's the variable ones (and the hidden ones) that tend to get away from them.

The cost nobody puts on the spreadsheet.

Here's the one that comes up most in conversations with owner-managed businesses: the owner's time.

If you run a business and you're delivering the work yourself, your time is a cost. It has a value. And if you're not factoring that in (properly, not just a nominal figure that looks reasonable on paper) then your margin numbers are lying to you.

I mentioned this last time around, but it bears repeating: £12,570 is not a living salary. Yet that's what plenty of owner-directors pay themselves on paper because it's tax-efficient. Fine for tax purposes.

Terrible for understanding whether your business actually works.

If you replaced yourself tomorrow, what would it cost? That's closer to the real number. And if your margins don't survive that calculation, you don't have a profitable business, you have a job that sends you invoices.

Cost creep: how to find it.

The exercise I'd encourage you to do is simple, though not always comfortable.

Go through every cost line by line. Not just the big ones. Everything. Ask three things about each one: Do I still need this? Am I getting value from it? When did I last check whether this is still the right price?

You will find things that have been quietly renewing for months, or years, that nobody has looked at. Software you don't use. Agreements you've outgrown. Supplier rates that made sense when you were smaller but haven't been renegotiated since.

You'll also find the things that genuinely earn their place, and knowing that is useful too.

Costs and pricing are a conversation, not two separate things.

This is the bit that pulls the miniseries together. Costs aren't just a number to minimise. They're the foundation of your pricing.

If you don't know what it actually costs you to deliver something, you cannot price it properly. You're guessing at the bottom of the equation and hoping the top holds up. Sometimes it does. Often enough, it doesn't and you only find out when the margin isn't there at the end of the month.

The business owners I see doing this well aren't necessarily the ones with the lowest costs. They're the ones who know their costs, have built them into their pricing, and revisit both regularly. That's it. That's the whole thing.

Three questions worth sitting with.

1. When did you last go through your costs line by line, not just the big items, but everything?
2. Do you have a real cost attached to your own time, or have you been quietly excluding yourself from the maths?
3. Is there a cost you've been meaning to look at but keep putting off, because looking at it might mean doing something about it?

If that third one made you think of something specific, that's probably where to start.

Closing the loop.

Margins are the output. Pricing and costs are the inputs. We've spent three months on all three, and if there's one thing I'd want you to take away from the whole series, it's this: none of it is as complicated as it feels when you avoid it. It's just a bit uncomfortable to look at.

The discomfort is the point. That's usually where the useful stuff is.

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