The initial cost for 6 plants is 1 x 6 pack @ $69 CAD, plus 1 extra coil now FREE, total initial cost = $69
Devices are guaranteed to last under normal use for 6 years.
Replacement coils during 6 years, about 3 x $15 = $45
Total spend over 6 years for 6 plants = $114
Cost per plant per season for 6 years = $3.17 CAD