Unless you approach Machu Picchu via the Inca Trail, all tourists going there MUST take the train from Cuzco or at least from Ollantaytambo to Aguas Calientes. Round trip, with only 30 kilometers each way, costs an incredible 57 USD per persons from Ollantaytambo in the backpacker train. The more comfortable Vistadome costs no less than 76 USD.