You can buy a ticket at gate 1 or gate 2. If you take the lift up Thủy Sơn, you buy the lift ticket as well. Children under 6 are free on all three tickets.
These are the prices on the management board's own price page. The city's fee change of August 2026 covered Hội An, Mỹ Sơn and the Chăm towers, not the Marble Mountains.