I don't think it is intended to be commercially viable on the basis of benzene production alone.

Rather, it is a more permanent solution compared to sequestration, where the benzene production offsets the cost.

If, as they plan, it can be done on-site, that would also eliminate transporting the soil and avoiding accidentally spreading it elsewhere, which is appealing as well.

Sanitary landfills (the sort that prevent seepage) are not exactly cheap either, and pose an ongoing risk in that the DDT is always there, waiting to get back out.