What the clueless authors at the Idiotic Regulations Suppliers don't know about their silly example, because they're not allowed to use AI:

Tour guides should generally be tipped at the very end of the tour, once services are completed, as a gesture of appreciation for their expertise and effort. In the U.S., a tip of 10–20% of the total tour cost is considered standard, though for short, high-quality tours, $10–$30 per day or $5–$20 per person is acceptable.

When and How to Tip

At the End: Always hand the tip directly to the guide at the conclusion of the tour, preferably in cash and inside an envelope or card.

For Multi-Day Tours: Tip the tour director at the end of the trip and local guides at the end of each specific, shorter, or day-long tour.

"Free" Tours: Even if a tour is advertised as "free," tipping is expected; $10–$20 per person is appropriate.