Your costs are mostly fixed
Rent, salaries and equipment cost the same whether a chair is full or empty. So a visit you win back adds its fee, less only the materials it uses, to your profit. Economists call that the contribution margin.
R900 fee − 10% materials = R810 to profit
Noam, Managing Media and Digital Organizations, §11.2.1.3, p.460
Money that waits costs money
A rand that arrives late is worth less. You either borrow to cover the gap at prime, or lose what it would have earned. This is the time value of money.
R10,000 × 10.75% × 45/365 = R133
Corelli, Analytical Corporate Finance, discounting, pp.44 to 46
People respond to a nudge
In a randomised trial at a dental practice, a plain reminder postcard more than doubled the share of overdue patients who booked a check-up within a month: 19.3% against 8.9%. After 100 days, 8.1 more in every 100 had actually come in.
Altmann and Traxler, European Economic Review 72 (2014), pp.19 to 38
Payback and present value
Any spend is judged two ways: how many months until it has paid for itself, and what its future rands are worth today, discounted at the rate you would pay to borrow. We show both, at prime.
Corelli, Analytical Corporate Finance, ch. 4: NPV p.122, payback p.126
A monthly leak grows; a once-off cost does not
With prices rising about 4% a year, every leak priced in rands grows with your fees. What you pay us is fixed the day you sign. That is why a once-off fix gets cheaper, in real terms, the longer you would have kept leaking.
Inflation forecast: SARB MPC statement, 23 Sep 2026