Dana or generosity is intrinsic to the 2500 year old Buddhist tradition. Since the time of Buddha, the teachings were considered priceless and thus offered freely. In keeping with this spirit, the teachers (resident and visiting) do not receive any payment for leading retreats even though they give generously of their time, energy and understanding. The daily accommodation tariff for retreats is set to cover expenses without profit. As the teachers receive no remuneration, they rely on the generosity of retreatants and friends who, appreciating the guidance that they receive, wish that this valuable work may continue.
There is a tendency in our culture to view giving as a personal loss or sacrifice. We sometimes give from a superior position to help those 'below' us in various ways. It is another perspective to see giving as an opportunity to cultivate the generous heart, and as a way of connecting with that which is good. In the Buddhist teachings the practice of dana is the foundation for awakening. There is no "right" amount that can be calculated in this spirit of giving. It is a response of heart, a personal choice that is entirely voluntary according to one's wishes and means.