I can live with the TPMS warning at startup for a couple of months if it means saving close to $200. I'll swap my sensors over when I get some nicer 17s for the warm weather, but for the winter tires, it's just not worth it to me. It's not going to hurt anything by running without the sensors.
2012 Focus Titanium Hatch-6/12/12 Build Date-Tux Black-Charcoal Cloth-DCT-Winter Pkg-Moonroof-K&N Drop-in-Magnaflow 15072
2014 Focus ST2-9/9/13 Build Date-Perf Blue-Charcoal/Blue Recaros-Moonroof-Cobb Intake-Magnaflow 15155-QuickLifts