"If I remember correctly the PT-6 conversion was priced at 1mil per engine."
Not sure what model PT6 is installed (PT6A-67?) but I would think a PT6 conversion today would be all of one million plus a big bucket more, per engine.
The Marsh S-2F3AT Turbo Tracker had Garrett TPE331s which may be a cheaper option?
Great military aircraft they were, but I can't imagine any cost effective commercial application for the piston or turbine Tracker, except as a rich kids rather impractical toy.