How to spend just 70$ for Machu Picchu
When I went to an agency in Cusco and asked about a trip to Machu Picchu, they told me the price was 140$. My jaw dropped, because I was expecting to spend just around 70$. In fact, if you do it on your own (and skip the middle-men), it’s possible.
So this is what you need to do:

Go to train station in Av. Pachacutec (the one, where train to Puno leaves from) and buy a ticket. The cheapest (for foreigners) costs 44$. Train goes from Ollantaytamba to Aquas Calientes. It leaves at 8 pm, return is at 5.45 am.

Ticket to Machu Picchu you can buy in Cusco in Instituto Nacional de Cultura (ca. San Bernardo), or at the entrance to the ruins. It costs 119 soles (for students S/.59 - with valid ISIC card)

Go to Ollantaytamba by bus. It leaves at 4 pm from station in Av. Grau and costs S/.5. You can also change bus in Urubamba.

Train leaves from Ollanta at 8 pm. Be at the station at least half hour earlier. It arrives in Aquas Calientes at 10 pm. It’s easy to find cheap hostel there.

To the ruins you can take a bus (6$ one-way) or go on foot.

All prices and information was actual in December 2006. More at howtoliveinperu.wordpress.com

Si llevas el Carne ISIC (International Student Identy Card) te haran un descuento del 50% en el ingreso. Este generalmente cuesta 120 Soles para los extranjeros, con el carne solo pagamos 60. Para mas info visita http://www.isic.org/

the souvenirs are cheaper here than in lima, bartering is easier too.  get lots of change from inside the bank before you go because it's easier to barter and they won't always have change.

Don't book ahead of time unless you are on an extreme time contstraint! Unless you are going on just a one week fly in and fly out vacation, don't book your Machu Picchu tour ahead of time, it will cost you twice as much money. Typically it is not hard to get on a trip within a week or two and if you book it while in Cusco you can get a room for under $10 a night ($3 a night if you like to travel like me) and get on a 4 day hike for under $300 ($160 if you are as good a bargainer as my friends and I are). If you book from outside of the country you could find yourself paying as much as $1000 for a hotel/hike deal. There are lots of day trips you can take out of cusco once you have booked your trip if you need to waste time for a week or so. Go to Puno and visit Lake Titicaca or go to Nazca to see the drawings on the earth.

WOW! Everyone should see this!!