On the trek to basecamp we stay in rustic teahouses or camp, at the organizers expense, so you do not have to pay. Here is some text from the Everest Basecamp Nepal Trek itinerary page :
Trek to Basecamp:
4) Walk to Namche Bazaar (3,450 metres/11,300 feet). Teahouse.
5) Rest and acclimatization in Namche. Teahouse.
6) Walk to Pangboche (3,750 metres/12,300 feet). Teahouse.
7) Walk to Pheriche (4,250 metres/13,900 feet). Visit the Himalayan Rescue Association health clinic. Teahouse.
8) Walk to Dugla (4,600 metres/15,100 feet). Teahouse.