The Cheapest Estimate Is the One That Costs You Most

Two plumbers get sent the same set of drawings.

The first one wants it quick and easy. He does not want to spend his evening working out what is actually in the job, and he does not want to pay anyone to do it for him either. So he rings a mate who did something similar and asks what he quoted. The mate says fifteen grand a unit. He writes fifteen grand a unit on the tender and sends it in. Done in five minutes, cost him nothing.

The second one does it properly. He either sits down and works the job out himself, or he pays someone to do the takeoff and pricing for him. It costs him some time or some money up front. He is fine with that, because he knows what happens on site when the number is wrong. Whatever takeoff software he uses only counts the quantities. The judgement about what is really in the job is still his.

Here is the part nobody wants to hear. The first plumber did not save money. He just moved the cost somewhere he cannot see it yet. And when it turns up, on site, halfway through the job, it is always bigger than what he would have spent getting the number right in the first place.

That is the false economy. The cheapest estimate is the one that costs you the most.

01What copying a mate's quote actually skips

When you copy a unit rate off someone else's job, you are assuming your job is the same as their job. It almost never is. And every difference between the two is a number you just failed to price.

Think about everything the five-minute quote never looked at. How many basements. Whether there is a stormwater pump station or a sewer pump station. How big the hot water plant is, and whether it is gas or one of the electric heat pumps that cost a lot more. Whether there is rainwater reuse. Whether there is gas at all.

None of that got checked. The number came off a phone call. So let me show you the specific traps, because these are the ones that quietly turn a "winning" price into a losing job.

02The materials moved since your mate's job

Supply prices change. The rate your mate got six months ago is not the rate you will pay today. Copper especially moves. If you priced off an old number, you have already lost money before you have picked up a tool.

03The builder mandates a dearer product than you assumed

You assumed PEX pipe. Then the builder says no, this job is specified in Rehau, which costs more than PEX. If you priced the cheap pipe and did not read the specification, you wear the difference. This is one of the most common ways people get caught. The spec said one thing, they priced another, and nobody hands the difference back to them.

04A high-end fitout is not a standard job

A luxury job is not the same as a standard job even when the fixture count looks identical. On a high-end job everything has to be perfect, tolerances are tight, and the work is slower.

The clearest example is the toilet. A standard close-coupled WC takes 45 minutes to an hour to install. An in-wall cistern WC on a high-end job takes around two hours, because of the carrier frame and all the in-wall work. That is double the labour, on every single WC in the job. Copy a standard rate onto an in-wall cistern job and you have quietly halved your own labour allowance without realising it.

05The fittings are dearer than you think

This is where stormwater and drainage quietly eat you alive. Take rainwater outlets. On a standard job you might be using a $90 outlet. On another job the design specifies a different model and that outlet is over $200 each. Now multiply that by twenty outlets. That is a swing of well over two thousand dollars on one item most people never even look at closely.

06The note hidden in the corner of the drawing

Cast iron pipe is a classic. You cannot just cast the pipe into the concrete and move on. It has to be lagged. That is extra material and extra labour. And then somewhere, in a note tucked into the corner of a drawing, it might say the lagging is not standard lagging but soundlag, which costs a lot more. If you missed that note, you missed the cost and the time. The plumber who read every note priced it. The one who copied a unit rate did not. If acoustic requirements are in play, our acoustic lagging takeoff is built for exactly this kind of hidden-in-the-notes cost.

Any one of these can turn a good-looking price into a loss. Stack two or three together and the mate's fifteen grand a unit was never going to cover it.

More on pricing and profit

07Related reading

• How to Actually Work Out Overheads in Your Plumbing Business (The Costs That Eat Your Profit)
• How to Estimate Plumbing Costs for Residential and Commercial Projects
• How Do I Avoid Pricing Mistakes That Eat Into My Profit?
• How Do I Price a Plumbing Job Correctly?

Here is the whole thing in one line. You cannot price what you have not looked at. Skipping the estimate does not remove those costs. It just hides them until site, where they cost you more.

08Spending money to make money

The plumber who wins the job and keeps his margin is not the cheapest one. He is the one who was willing to invest in getting the number right, whether that meant spending his own hours on a proper takeoff, or paying someone to do it for him.

That is not being a big spender. That is understanding where the real risk sits. A few hours or a few hundred dollars spent getting the estimate right is cheap insurance against thousands lost on site when the missed costs turn up. The plumber who refuses to spend anything on the estimate is not saving money. He is gambling, and the drawings always know something he does not. It is the same reason so many hard-working plumbers stay busy without ever actually getting ahead.

It is the same discipline behind every job on our case studies page. Open the drawings. Read every note. Count every fitting. Price the actual products specified. Build the number up from what is really there.

09Where we come in

Working the job out properly takes time, and time is the one thing a plumber running jobs does not have. That is what we do. We open the drawings, we do the full takeoff, we price the real materials and the real labour for the fixtures actually specified, and we build you a number you can stand behind. You can see how it works on our hydraulic estimating service page.

And if there is underground pipework, the trench side is where a lot of the cost hides. That is where our civil and stormwater estimating and the free calculator below earn their keep.

Pricing a job with underground pipework?
Our free bedding and spoil calculator handles the part most takeoff software leaves out. Bedding, embedment, trench fill and spoil in m³ and tonnes, with truck loads worked out.

Send us your drawings. Get a number you can stand behind.

Email us the drawings and we will come back with a fully itemised estimate that reflects the real scope of your job, not someone else's.

Because the goal was never just to win the tender. It is to win it at a price you can actually deliver.

This article reflects the author's professional experience in hydraulic estimating across Australia. Pricing examples are indicative only and will vary by project, specification, supplier and market conditions at the time of tender. Always price from the actual drawings and specification for your specific job. Last updated 1 July 2026.