The $25 per day is what the guide gets paid for 2 clients or less the rate goes up slightly with more trekkers. In addition to wages, other charges include: insurance for the guide ($30 per trip), Sherpana Fee (per day charge that varies slightly with number of people + 20% of the permit cost). For treks that require flights a transport fee is included (currently $90 each way for Lukla flights).
You can see a breakdown of the fees for the trek by going to the itinerary page. Click the button to see a breakdown of the price. Sherpana fees are included in the guide rate per day and the permits. Before you pay you will be able to see an exact breakdown of all the fees, wages, ect, so you know exactly where the money is going.
To adjust the price to a different number of people click the ‘trekkers’ button at the top of the page and set the number of trekkers in your group. The prices will be automatically updated for the number of trekkers entered. It is required that your browser ‘cookies’ must be enabled to use this feature.