The system allows tracking costs for exact search. For example, if you are looking for a particular amount of flight in a precise location, just set a price alert and they will send you an email if there is a notable change in rate. Moreover, Momondo offers many options to filter search.
This is the largest Home Exchange platform in the world. We used it and exchanged our apartment with a family from Paris and had an amazing two week long vacation. We highly recommend to check and to use this platform.