Are there any extra fees on top of the price?
No. The total price on the booking page is what you pay for your package. It includes everything listed under "Included" on the package page. Items listed under "Not included" (for example international flights, some meals, tips and personal expenses) are not part of the price.
The only optional charge is the 15% card payment fee if you choose to pay the balance by card instead of in cash on day 1. It is shown before you pay.