How many people are in your group? Tour operators usually charge by the person and they usually want a minimum of 4 people. If you try booking online some "booking engines" will automatically calculate the 4 person price even if you have only 2 people in your party so it might be better to contact the tour operator directly so they can pair you up with others.

We just got back from Dominica and spent anywhere from around $50US to $95US per person depending on the length of the hike.

Google "Dominica hiking tours" for lots of links - here's just one: www.khattstours.com