A commodity like ME always fluctuates, but there are a couple disturbing trends at play here. First, all recent VU changes have all effected sweat availability in a negative way. Second, resellers are now hanging in popular sweating places and killing the sweating mobs so they can inflate prices. And not to sound like your grandparents, but today's sweaters are lazy. The rates they get for sweat are so high that they don't feel motivated to chase mobs anymore. 22-25 pec per successful sweating attempt.
It will be up to
MA to implement a change to increase sweat availability, making MindForce usable once again. Until then, the MF market will stay depressed, and only the wealthiest will touch it.