Don’t know where you live, but here in NC propane is around $3.32 per gallon[0], equivalent to $3.60 per therm. My last natgas bill was $1.38/therm, almost a third the cost. In fact, propane is much closer in cost (per BTU equivalent) to fuel oil than natural gas.
For natural gas, is that only some itemized procurement price, or full price as delivered?
In the SF Bay Area, our last PG&E bill split across Jan/Feb was effectively $3.05/therm. The actual pricing in our bill reflects tiered pricing, with different tier thresholds in each month. The first tier covers up to 2 therms/day in Jan and 1.48 therms/day in Feb. The price tiers were $2.68..$3.06/therm in Jan and $2.75..$3.14/therm in Feb.
The bill also described $1.37/therm and $1.44/therm procurement prices for Jan and Feb, respectively.
Damn, I just got my propane tank refilled - it's a tiny 125 gallon one, mostly backup for our wood stove. We paid something like $2.40, and that's only because we didn't get a bulk discount most people get when they fill up the larger tanks sized for primary heat for a full season.
[0] https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=W...