For me the Salkantay Trek of 5 days was a unique experience. The change of the nature during the trip is amazing. It goes from almost desert zone until tropical jungle and finally Machupicchu is unique to visit and was my personal highlight.
Thanks to the good information our group was really first in Machupicchu and could spend some minutes there without any other tourists. I think it was worth to spend quite a high amount of money for the trip. Everything was perfect organized.
The guide David was just amazing.
You feel that he loves his job. As well the food and the camping accommodations where very good and delightful. So just go for it!