Is $180 to purchase Broan QTXE110S-B replacement kit a fair price?

I inherited a QTXE110S-B unit that is always on, despite the relative humidity being 28% and the control setting at 80%. I tried to remove the pictured sensor and harness, which were severely corroded. I'm looking for options to get just the board itself, as Broan sells the part with the controller, grille assembly, and harness for $180 shipped, and new fans with no controller are priced similarly. I'm also wondering if replacing the switch with a humidity sensor switch would work with this unit. If I try the in-wall sensor, the Broan wiring shows an orange wire from the controller to a black wire for automatic mode, but I'm not sure if my wiring is set up like that as I haven't opened up the junction box or taken the unit out. I suspect it may be wired at the blower unit itself. It would be a two-stage replacement to wire in the switch and then disconnect the hardwire to the old controller, or I could leave the old controller in its disconnected state. I'm wondering if that's feasible.