My filter pitcher reminds me via SMS to replace the cartridge costing 400 rubles)

It seems like the price is tiny and there's no point in bothering with organizing a service, people aren't fools, they'll replace it themselves...

But no.
Smart business knows that a repeat sale is 20 times cheaper than the first one, and a 3% increase in average check boosts profit growth by 20%.

Let's take an example and take care of the average check and the number of sales per year.