Take time to choose your trekking company. The cheapest trekking company may not always be the best, and the most expensive may be overcharging for the service. The Inca trail is not cheap, as packages that travel agents offer include: Inca trail permits ($90), entrance to Machu Picchu ($45), transport to the trail head, a return train and transport to Cusco ($30-50), all your meals and snacks, porters, cooking and camping equipment.
Ask your trekking company how they look after their porters, as in the past companies have been accused of treating their porters unfairly.
A fair price in 2010 for the full 4 days Inca Trail is US $400 – $500.