Although it is relatively cheap here in Peru. As usual the touristy things the `prices have skyroketted over the last 2 years. Talking to a local, these trails were much cheaper just 3 years ago before the tourist boom.
Prices vary widely, so I suggest that you take the time to walk around and talk to as many agents as possible. They often offer the same things exactly for different prices. Student cards often get a bit of a discount.
The main Inca Tour of 4days/3nights is often fully booked out. This will need a reservation of about 2 months advance. This is the most popular trail and the most expensive at around 800USD per person. This is booked out since now you MUST hçgo by tour guide and the local government have imposed a 500person max per day. However the porters and guides often take up nearly half that number.
The Inca Jungle tour is the next popular. 4day/3night. No advance booking needed and costs alot less. You can attain this for 160USD if you bargin enough. The difference is you don´t take the whole trail of all the ruins. You do some other adventure and nature things with the jungle surrounding. However you do end at Machupicchu for a full day there. No camping here all hostel stays.
The Salkantay tour is another good one. 5day/4nights of all camping around the mountains. You will climb alot here so careful to choose this. This is also better in the drier months of June-Sept. As it gets very cold otherwise at night with all the rain.
All these tours will include most meals, camping equipment like tents and mats. Not sleeping bags. Guide (lucky if in English).
We have been advised that Malaria tablets are not needed here. However water purifying tablets are. It is also suggested you take 3-4 days to adjust to the altitude. IT is true that it is HARD. Even the most supreme athlete has a hard time with the sudden change of height.
Other day tours are Sacred Valley (20 SOL each) ruins around the valley area and visit to different little towns, markets. City Tours for 15 SOL each and is also for ruins near the Cuzco city but you can also walk this sites rather than get a tour.
You can do horseback riding for 30 SOL. Just a half day in Machupicchu or a 2 day/1 night at Machupicchu for 160USD.
Entrance for the Machupiccu alone is 43USD or 23 for student. The trains from Cuzco return is about 60USD for the 2nd class. The train takes you to Aguas Calientes where you can either walk to the mountain or take a bus for 13USD each. The walk is about 2 hours.
Most taxis and buses are cheap. Except for the bus to Machupiccu as this is a British run company. The local buses between cities is around 5SOL.
Other than ruins there is also many natural hot springs to visit, little villages, and markets. There is plenty to do here. There is also good connections to other major cities like Puno(Lake Titicaca).
Shop around for buses to other town. The tour agents take a lot of extra cash. I prefer Cruz del Sur and their direct website is www.cruzdelsur.com.pe
Hope this is helpful.