I did the trail in March and booked it a day after arriving in Cusco. Just walked down Gringo alley and stopped in at a few tour outfits to get prices and find out what was included. After checking about 10 outfits, I decided on the one that was 2nd cheapest. Sort of like choosing a cheap hotel, you don't want the bottom of the barrel, but close to it.

Something to note is that I had to wait 3 days after booking the hike because the government has to approve your being on the trail and the standard wait is 3 days if you book monday to wednesday. Longer for other days because of the weekend. I booked on a wednesday and started the trail the following saturday.
The 4 day tour cost me $160 USD and was pretty good overall, including everything but a bag to sleep in. You can come to my pod and read aboot it if you like.
The Inca Trail: prepare for rainbtw, I bargained for the sleeping bag rental and got one for $5 rather than the $10 they were asking for at the tour office. The time to bargain is when you're rubbing your chin and making up your mind, not after you've handed them the cash. My tentmate on the tour got an even better deal than me, demanding they rent him their best sleeping bag for
free, which they did. It was a tiny thing and kept him warm on the coldest night while fitting into his backpack while hiking. He also only paid $150 for the hike. grrr...
I finished the trail about a week before the slide that blocked it. My friend was about to do that last day on the trail when word came that the slide had happened the night before during heavy rain. He also endured pouring rain for almost the entire hike. Oh well, I had a good time.