There are two types of tips, the staff tip, and the summit-attempt bonus.
The "staff tip" will be $100 per foreign climber. Expect to pay this tip no matter what.
For the "summit-attempt bonus" a group Sherpa who helps you to climb up to the the high camp or up to the summit and back down, expect to pay $50, £25, €40 per sherpa. That amount of money may be split between the climbers in the summit party.
We request you to bring this money with you to Tibet, in cash, and be ready to pay it there, as many of our staff are Tibetan and will not be returning to Kathmandu with us. Travelers cheques and credit cards may be of use in Kathmandu, but they will not work in Tibet.