Can't speak for going around the town to bargain for different prices, but we booked through our hostel (Boulevard) for 40 soles. You can definitely get it cheaper, but you don't stay out as long. We got to go down three dunes, which will give you your adrenaline fix for a year because of how damn fast you go. The dune buggies are also insane, especially if you sit in the back. Seriously. They're nuts. But we ended the evening drinking beer and wine and watching the sunset. Totally worth the back and neck pains (and skinned arms) while in Huacachina. #extreme