Have a look at something like www.cash****rewards.com.
Take away the asterix.
You will earn a small amount back by giving the company providing the service your business and your data.
Like a lot of people love FB/EDR, we are giving them our spending and data, they give us back points.
Credit card companies give you points, but they earn from you putting your purchase via them.
Etc, etc, etc.
Also, some travel websites will offer maybe 90% of the price, or 95% if you book flights and hotel and car rentals direct with them, they get your money when you spend with them, and they drop the prices of the whole trip with them.
QF and the other airlines do this too, if you book air and hotels with QF, they promise a discount in hotel.
Eg; if you book a flight on the QF website, you get the eticket email, but a while later, QF will send you another email, asking that you book hotel and go via the link in that email, so you get a bit off the hotel booking price.