You are correct, we are fulltiming and pay electric. For us the additional monthly cost was similar to running one AC unit in the summer. The biggest benefit was never having to worry you’d run low or ultimately out of propane — no more hauling heavy bottles!
For me, this is the best part of all - no propane tank schlepping. Those 40 pounders are super-heavy. 30's are a bit lighter but still - no fun.
My current tiny-trailer has two 20's. Easy! That said, my Cheap Heat is an AC-power only unit. And we use an induction cooktop for cooking. So our tanks last one to two seasons, using it only for the water heater when we want quick recovery or if we're boondocking or if we're on 30A shore power and need that power for Cheap Heat or air conditioning.