We watch pages . By hand you would get to them , at seconds a page, and % of the time something changed. Whoever does it earns $ a year.
Checking 25 pages once a day is 750 checks a month at 120 seconds each, or 25 hours, worth $685 a month at $60,000 a year ($28.85 an hour over 2,080 working hours). The 38 changes PageCrawl finds still need reading, so they stay in the total; what you get back is the 712 checks that would have found nothing. PageCrawl checks the same pages 24 times as often, and the plan price is the annual rate.