A discount reduces the price without reducing any of the cost, so all of it comes out of profit.
The arithmetic nobody does at the time
On a thirty per cent gross margin, a ten per cent discount removes a third of the profit on that job. Replacing it takes fifty per cent more volume at the same margin.
The lower the margin, the worse it gets. At twenty per cent margin, a ten per cent discount halves the profit.
This is the mirror of raising prices, and it is why a small concession feels minor and is not.
What it teaches the customer
That the first price was not the real one. A customer who receives a discount once expects it again, and the discount becomes the price.
It also invites the comparison the business least wants: if the price could move, the question becomes how far.
Where discounting is legitimate
Volume that genuinely lowers cost — several jobs at one location, work scheduled to fill a quiet period. The cost really does fall, so the margin is protected.
Prompt payment, where the value of being paid immediately is real — see days to get paid.
Deliberate entry pricing on a first job with a customer worth having, taken with the margin known and the intention stated.
Each of these is a decision with a reason. What is expensive is the discount given at the door to avoid an uncomfortable conversation.
Alternatives that cost less
Reducing scope rather than price, so the lower figure buys less.
Adding something with a low cost and a visible value.
Offering options rather than a single number, which moves the conversation from whether to which — see proposals.
Tracking it
Discounts recorded against the job rather than absorbed into the price. Absorbed, they appear as a margin problem with no visible cause, and nobody can tell whether the business is underpricing or over-discounting.